<p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;"ul> <bli>Deoxyribonucleic acidDeoxyriboNucleic Acid</bli>&nbsp;( <bli>DNANucleotide : a Base + deoxy ribo sugar + phosphate.</bli>) <li>Nucleotides are arranged in two long double strands that form a double helix structure.</li> <li>DNA is a molecule that encodes thehereditary material. Double helix structure(discovered by Watson&nbspamp;Crick)<a href="http://enli> <li>Information of DNA is based on its sequence.wikipediaDNA sequence consists Adenine(A), Guanine(G), Cytosine(C), T(Thymine).org</wiki/Genetics" title="Genetics" style="textli> <li>Watson-decorationCrick DNA base pair : none; color: rgb(11A-T, 0, 128); backgroundG-image: none;"C</li> <li>geneticCan replicate, repair.</ali>&nbsp;instructions used in the development and functioning of all known living&nbsp; <li>DNA transcribed into RNA, RNA translated into Protein.<a href="http:/li> <li>DNA is organized into chromosome structure.</en.wikipedia.orgli> <li>&nbsp;</wikili></Organism" title="Organism" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"ul>organisms </ap>&nbsp;and many</p> <p>&nbsp;<a href="http:/p> <p>&nbsp;</en.wikipedia.orgp> <p><strong>Deoxyribonucleic acid</wikistrong>&nbsp;(<strong>DNA</Virus" titlestrong>) is a molecule that encodes the&nbsp;<a href="Virus" http://en.wikipedia.org/wiki/Genetics" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetics">virusesgenetic</a>. Along with&nbsp;instructions used in the development and functioning of all known living&nbsp;<a href="http://en.wikipedia.org/wiki/RNAOrganism" title="RNA" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Organism">RNAorganisms</a>&nbsp;andmany&nbsp;<a href="http://en.wikipedia.org/wiki/Proteins" title="Proteins" class="mw-redirectVirus" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Virus">proteinsviruses</a>, DNA is one of the three major. Along with&nbsp;<a href="http://en.wikipedia.org/wiki/Macromolecules" title="Macromolecules" class="mw-redirectRNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="RNA">macromoleculesRNA</a>&nbsp;essential for all known forms of&nbspand&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Life" title="LifeProteins" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Proteins">lifeproteins</a>. Most , DNA molecules are double-stranded helices, consisting of two long&nbsp;is one of the three major<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Biopolymer" title="BiopolymerMacromolecules" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Macromolecules">biopolymersmacromolecules</a>&nbsp;essential for all known forms of simpler units called&&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleotide" title="NucleotideLife" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Life">nucleotideslife</a>. Most DNA molecules are double-stranded helices, consisting of two long&mdashnbsp;each nucleotide is composed of a&nbsp;<a <a href="http://en.wikipedia.org/wiki/Nucleobase" title="NucleobaseBiopolymer" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Biopolymer">nucleobasebiopolymers</a>&nbsp;(of simpler units called&nbsp;<a href="http://en.wikipedia.org/wiki/Guanine" title="GuanineNucleotide" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleotide">guaninenucleotides</a>,&mdash;each nucleotide is composed of a&nbsp;<a href="http://en.wikipedia.org/wiki/Adenine" title="AdenineNucleobase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleobase">adeninenucleobase</a>,&nbsp;(<a href="http://en.wikipedia.org/wiki/Thymine" title="ThymineGuanine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Guanine">thymineguanine</a>, and&nbsp;<a href="http://en.wikipedia.org/wiki/Cytosine" title="CytosineAdenine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Adenine">cytosineadenine</a>), recorded using the letters G, A, T, and C, as well as a&nbsp;<&nbsp;<a href="http://en.wikipedia.org/wiki/Backbone_chain" title="Backbone chainThymine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Thymine">backbonethymine</a>, and&nbsp;made of alternating<a href="http://en.wikipedia.org/wiki/Monosaccharide" title="MonosaccharideCytosine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cytosine">sugarscytosine</a>), recorded using the letters G, A, T, and C, as well as a&nbsp;(<a href="http://en.wikipedia.org/wiki/DeoxyriboseBackbone_chain" title="Deoxyribose" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Backbone chain">deoxyribosebackbone</a>) and&nbsp;made of alternating<a href="http://en.wikipedia.org/wiki/Phosphate" title="PhosphateMonosaccharide" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Monosaccharide">phosphatesugars</a>&nbsp;groups (related to&nbsp;<a href="http://en.wikipedia.org/wiki/Phosphoric_acid" title="Phosphoric acidDeoxyribose" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Deoxyribose">phosphoric aciddeoxyribose</a>), with the nucleobases (G, A, T, C) attached to the sugarsand&nbsp;<a href="http://en.wikipedia. DNA is wellorg/wiki/Phosphate" style="text-suited for biological information storagedecoration: none; color: rgb(11, since the DNA backbone is resistant to cleavage and the double0, 128); background-stranded structure provides the molecule with image: none;" title="Phosphate">phosphate</a built-in duplicate of the encoded information.>&nbsp;groups (related to&nbsp;</p><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Phosphoric_acid" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="Phosphoric acid">The two strands of DNA run in opposite directions to each other and are therefore&nbsp;<phosphoric acid</a href="http://en.wikipedia.org/wiki/Antiparallel_(biochemistry>)" title="Antiparallel , with the nucleobases (biochemistry)" style="text-decoration: none; color: rgb(11G, A, 0T, 128C); background-image: none;">antiattached to the sugars. DNA is well-parallel</a>suited for biological information storage, one since the DNA backbone being 3&prime; (three prime) is resistant to cleavage and the other 5&prime; (five prime). This refers to double-stranded structure provides the direction molecule with a built-in duplicate of the 3rd and 5th carbon on the sugar molecule is facingencoded information. Attached </p> <p>The two strands of DNA run in opposite directions to each sugar is one of four types of molecules called nucleobases (informally,other and are therefore&nbsp;<i>bases</i>). It is the<a a href="http://en.wikipedia.org/wiki/Nucleic_acid_sequence" title="Nucleic acid sequenceAntiparallel_(biochemistry)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Antiparallel (biochemistry)">sequenceanti-parallel</a>&nbsp, one backbone being 3&prime;of these four nucleobases along (three prime) and the backbone that encodes genetic informationother 5&prime; (five prime). This information is read using refers to thedirection the 3rd and 5th carbon on the sugar molecule is facing. Attached to each sugar is one of four types of molecules called nucleobases (informally,&nbsp;<a href="http:em>bases</em>). It is the<a href="http://en.wikipedia.org/wiki/Genetic_code" title="Genetic codeNucleic_acid_sequence" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleic acid sequence">genetic codesequence</a>, which specifies the sequence of the&nbsp;of these four nucleobases along the backbone that encodes genetic information. This information is read using the&nbsp;<a href="http://en.wikipedia.org/wiki/Amino_acid" title="Amino acidGenetic_code" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic code">amino acidsgenetic code</a>&nbsp;within proteins. The code is read by copying stretches , which specifies the sequence of DNA into the related&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleic_acid" title="Nucleic acidAmino_acid" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Amino acid">nucleic acidamino acids</a>&nbsp;RNA in a process calledwithin proteins. The code is read by copying stretches of DNA into the related&nbsp;<a href="http://en.wikipedia.org/wiki/Transcription_(genetics)" title="Transcription (genetics)Nucleic_acid" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">transcriptiontitle="Nucleic acid">nucleic acid</a>.&nbsp;RNA in a process called&nbsp;</p><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Transcription_(genetics)" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="Transcription (genetics)">transcription</a>.</p> <p>Within cells, DNA is organized into long structures called&nbsp;<a href="http://en.wikipedia.org/wiki/Chromosome" title="Chromosome" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chromosome">chromosomes</a>. During&nbsp;<a href="http://en.wikipedia.org/wiki/Cell_division" title="Cell division" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cell division">cell division</a>&nbsp;these chromosomes are duplicated in the process of&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_replication" title="DNA replication" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA replication">DNA replication</a>, providing each cell its own complete set of chromosomes.&nbsp;<a href="http://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Eukaryote">Eukaryotic organisms</a>&nbsp;(<a href="http://en.wikipedia.org/wiki/Animal" title="Animal" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Animal">animals</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Plant" title="Plant" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Plant">plants</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Fungus" title="Fungus" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Fungus">fungi</a>, and&nbsp;<a href="http://en.wikipedia.org/wiki/Protist" title="Protist" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Protist">protists</a>) store most of their DNA inside the&nbsp;<a href="http://en.wikipedia.org/wiki/Cell_nucleus" title="Cell nucleus" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cell nucleus">cell nucleus</a>&nbsp;and some of their DNA in<a href="http://en.wikipedia.org/wiki/Organelle" title="Organelle" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Organelle">organelles</a>, such as&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mitochondria" title="Mitochondria" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Mitochondria">mitochondria</a>&nbsp;or&nbsp;<a hrefclass="mw-redirect" href="http://en.wikipedia.org/wiki/Chloroplasts" title="Chloroplasts" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chloroplasts">chloroplasts</a>.<sup id><a href="cite_ref-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://enhttp://en.wikipedia.org/wiki/DNA#cite_note-1" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[1]</a></sup>&nbsp;In contrast,&nbsp;<a href="http://en.wikipedia.org/wiki/Prokaryote" title="Prokaryote" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Prokaryote">prokaryotes</a>&nbsp;(<a href="http://en.wikipedia.org/wiki/Bacteria" titlestyle="Bacteria" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bacteria">bacteria</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Archaea" title="Archaea" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Archaea">archaea</a>) store their DNA only in the&nbsp;<a href="http://en.wikipedia.org/wiki/Cytoplasm" title="Cytoplasm" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cytoplasm">cytoplasm</a>. Within the chromosomes,&nbsp;<a href="http://en.wikipedia.org/wiki/Chromatin" title="Chromatin" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Chromatin">chromatin</a>&nbsp;proteins such as&nbsp;<a href="http://en.wikipedia.org/wiki/Histone" title="Histone" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Histone">histones</a>&nbsp;compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">The obsolete synonym &quot;<b>desoxyribonucleic acid</b>&quot; may occasionally be encountered, for example, in pre-1953 genetics.</p><div ;<strong>desoxyribonucleic acid</strong>&quot; may occasionally be encountered, for example, in pre-1953 genetics.</p> <div class="toc tochidden" id="toc" class="toc tochidden" style="border: 1px solid rgb(170, 170, 170); background-color: rgb(249, 249, 249); padding: 7px; display: inline-block; zoom: 1; font-family: sans-serif; line-height: 19.200000762939453px;">

<h2 style="background-image: none; margin: 0px 0px 0.6em; overflow: hidden; padding: 0px; border: none; font-size: 12px; display: inline;">Contents</h2>&nbsp;<span class="toctoggle" style="-webkit-user-select: none; font-size: 11.199999809265137px;">&nbsp;[<a class="internal" href="http://en.wikipedia.org/wiki/DNA#" class="internal" id="togglelink" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">show</a>]&nbsp;</span></div>

 <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Properties">Properties</span></h2> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 302px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:DNA_chemical_structure.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/DNA_chemical_structure.svg/300px-DNA_chemical_structure.svg.png" widthstyle="300" height="350" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e4/DNA_chemical_structure.svg/450pxbackground-DNA_chemical_structure.svg.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/e/e4/DNA_chemical_structure.svg/600px-DNA_chemical_structure.svg.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:350px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);300px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:DNA_chemical_structure.svg" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>Chemical structure of DNA.&nbsp;<a href="http://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydrogen bond">Hydrogen bonds</a>&nbsp;shown as dotted lines.</div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">DNA is a long&nbsp;<a href="http://en.wikipedia.org/wiki/Polymer" title="Polymer" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Polymer">polymer</a>&nbsp;made from repeating units called&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleotide" title="Nucleotide" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleotide">nucleotides</a>.<sup id="cite_ref-2" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-2" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[2]</a></sup><sup id><a href="cite_ref-Alberts_3-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://http://en.wikipedia.org/wiki/DNA#cite_note-Alberts-3" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[3]</a></sup><sup id><a href="cite_ref-Butler_4-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://http://en.wikipedia.org/wiki/DNA#cite_note-Butler-4" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4]</a></sup>&nbsp;DNA was first identified and isolated by&nbsp;<a href="http://en.wikipedia.org/wiki/Friedrich_Miescher" title="Friedrich Miescher" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Friedrich Miescher">Friedrich Miescher</a>&nbsp;and the double helix structure of DNA was first discovered by&nbsp;<a href="http://en.wikipedia.org/wiki/James_Watson" title="James Watson" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="James Watson">James Watson</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Francis_Crick" title="Francis Crick" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Francis Crick">Francis Crick</a>. The structure of DNA of all species comprises two helical chains each coiled round the same axis, and each with a pitch of 34&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/%C3%85ngstr%C3%B6m" titlestyle="&Aring;ngstr&ouml;m" class="mw-redirect" style="text-decorationtext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ångström">&aring;ngstr&ouml;ms</a>&nbsp;(3.4&nbsp;<a href="http://en.wikipedia.org/wiki/Nanometre" title="Nanometre" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nanometre">nanometres</a>) and a radius of 10&nbsp;&aring;ngstr&ouml;ms (1.0&nbsp;<a href="http://en.wikipedia.org/wiki/Nanometre" title="Nanometre" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nanometre">nanometres</a>).<sup id="cite_ref-FWPUB_5-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-FWPUB-5" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5]</a></sup>&nbsp;According to another study, when measured in a particular solution, the DNA chain measured 22 to 26&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/%C3%85ngstr%C3%B6m" titlestyle="&Aring;ngstr&ouml;m" class="mw-redirect" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ångström">&aring;ngstr&ouml;ms</a>&nbsp;wide (2.2 to 2.6&nbsp;<a href="http://en.wikipedia.org/wiki/Nanometre" title="Nanometre" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nanometre">nanometres</a>), and one nucleotide unit measured 3.3&nbsp;&Aring; (0.33&nbsp;nm) long.<sup id><a href="cite_ref-6" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-6" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[6]</a></sup>&nbsp;Although each individual repeating unit is very small, DNA polymers can be very large molecules containing millions of nucleotides. For instance, the largest human&nbsp;<a href="http://en.wikipedia.org/wiki/Chromosome" title="Chromosome" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chromosome">chromosome</a>, chromosome&nbsp;<a href="http://en.wikipedia.org/wiki/Chromosome_1_(human)" titlestyle="Chromosome 1 (human)" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chromosome 1 (human)">number 1</a>, consists of approximately 220 million&nbsp;<a href="http://en.wikipedia.org/wiki/Base_pair" title="Base pair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Base pair">base pairs</a><sup id><a href="cite_ref-7" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:http://en.wikipedia.org/wiki/DNA#cite_note-7" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[7]</a></sup>&nbsp;and is 85&nbsp;mm long.</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In living organisms DNA does >In living organisms DNA does not usually exist as a single molecule, but instead as a pair of molecules that are held tightly together.<sup id><a href="cite_ref-autogenerated2_8-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-autogenerated2-8" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[8]</a></sup><sup id><a href="cite_ref-berg_9-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://http://en.wikipedia.org/wiki/DNA#cite_note-berg-9" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[9]</a></sup>&nbsp;These two long strands entwine like vines, in the shape of a&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Double_helix" titlestyle="Double helix" class="mw-redirect" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Double helix">double helix</a>. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a nucleobase, which interacts with the other DNA strand in the helix. A nucleobase linked to a sugar is called a&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleoside" title="Nucleoside" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleoside">nucleoside</a>&nbsp;and a base linked to a sugar and one or more phosphate groups is called a&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleotide" title="Nucleotide" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">nucleotidetitle="Nucleotide">nucleotide</a>. A polymer comprising multiple linked nucleotides (as in DNA) is called a&nbsp;<a href="http://en.wikipedia.org/wiki/Polynucleotide" title="Polynucleotide" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Polynucleotide">polynucleotide</a>.<sup id="cite_ref-IUPAC_10-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-IUPAC-10" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[10]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">The backbone of the DNA strand is made from alternating&nbsp;<a href="http://en.wikipedia.org/wiki/Phosphate" title="Phosphate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Phosphate">phosphate</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Carbohydrate" title="Carbohydrate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Carbohydrate">sugar</a>&nbsp;residues.<sup id="cite_ref-Ghosh_11-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Ghosh-11" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[11]</a></sup>&nbsp;The sugar in DNA is&nbsp;<a href="http://en.wikipedia.org/wiki/Deoxyribose" title="Deoxyribose" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Deoxyribose">2-deoxyribose</a>, which is a<a href="http://en.wikipedia.org/wiki/Pentose" title="Pentose" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Pentose">pentose</a>&nbsp;(five-<a href="http://en.wikipedia.org/wiki/Carbon" title="Carbon" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Carbon">carbon</a>) sugar. The sugars are joined together by phosphate groups that form&nbsp;<a href="http://en.wikipedia.org/wiki/Phosphodiester_bond" title="Phosphodiester bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Phosphodiester bond">phosphodiester bonds</a>&nbsp;between the third and fifth carbon&nbsp;<a href="http://en.wikipedia.org/wiki/Atom" title="Atom" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Atom">atoms</a>&nbsp;of adjacent sugar rings. These asymmetric&nbsp;<a href="http://en.wikipedia.org/wiki/Covalent_bond" title="Covalent bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Covalent bond">bonds</a>&nbsp;mean a strand of DNA has a direction. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are<iem>antiparallel</iem>. The asymmetric ends of DNA strands are called the&nbsp;<a href="http://en.wikipedia.org/wiki/Directionality_(molecular_biology)" title="Directionality (molecular biology)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Directionality (molecular biology)">5&prime;</a>&nbsp;(<iem>five prime</iem>) and&nbsp;<a href="http://en.wikipedia.org/wiki/Directionality_(molecular_biology)" titlestyle="Directionality (molecular biology)" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Directionality (molecular biology)">3&prime;</a>&nbsp;(<iem>three prime</iem>) ends, with the 5&prime; end having a terminal phosphate group and the 3&prime; end a terminal hydroxyl group. One major difference between DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the alternative pentose sugar&nbsp;<a href="http://en.wikipedia.org/wiki/Ribose" title="Ribose" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ribose">ribose</a>&nbsp;in RNA.<sup id="cite_ref-berg_9-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-berg-9" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[9]</a></sup></p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 172px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:DNA_orbit_animated_static_thumb.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/db/DNA_orbit_animated_static_thumb.png/170px-DNA_orbit_animated_static_thumb.png" widthstyle="170" height="316" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/d/db/DNA_orbit_animated_static_thumb.png 1.5xbackground-color:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/d/db/DNA_orbit_animated_static_thumb.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:316px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);170px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:DNA_orbit_animated_static_thumb.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>A section of DNA. The bases lie horizontally between the two spiraling strands.<sup id="cite_ref-12" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-12" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[12]</a></sup>(<a href="http://en.wikipedia.org/wiki/File:DNA_orbit_animated.gif" title="File:DNA orbit animated.gif" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="File:DNA orbit animated.gif">animated version</a>).</div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">The DNA double helix is stabilized primarily by two forces:&nbsp;<a href="http://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydrogen bond">hydrogen bonds</a>&nbsp;between nucleotides and&nbsp;<a href="http://en.wikipedia.org/wiki/Stacking_(chemistry)" title="Stacking (chemistry)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Stacking (chemistry)">base-stacking</a>&nbsp;interactions among&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Aromatic" title="Aromatic" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Aromatic">aromatic</a>&nbsp;nucleobases.<sup id="cite_ref-Yakovchuk2006_13-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Yakovchuk2006-13" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[13]</a></sup>&nbsp;In the aqueous environment of the cell, the conjugated&nbsp;<a href="http://en.wikipedia.org/wiki/Pi_bond" title="Pi bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">&title="Pi bond">&pi; bonds</a>&nbsp;of nucleotide bases align perpendicular to the axis of the DNA molecule, minimizing their interaction with the&nbsp;<a href="http://en.wikipedia.org/wiki/Solvation_shell" title="Solvation shell" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Solvation shell">solvation shell</a>&nbsp;and therefore, the&nbsp;<a href="http://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Gibbs free energy">Gibbs free energy</a>. The four bases found in DNA are&nbsp;<a href="http://en.wikipedia.org/wiki/Adenine" titlestyle="Adenine" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Adenine">adenine</a>&nbsp;(abbreviated A),&nbsp;<a href="http://en.wikipedia.org/wiki/Cytosine" title="Cytosine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cytosine">cytosine</a>&nbsp;(C),&nbsp;<a href="http://en.wikipedia.org/wiki/Guanine" title="Guanine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Guanine">guanine</a>&nbsp;(G) and&nbsp;<a href="http://en.wikipedia.org/wiki/Thymine" title="Thymine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Thymine">thymine</a>&nbsp;(T). These four bases are attached to the sugar/phosphate to form the complete nucleotide, as shown for&nbsp;<a href="http://en.wikipedia.org/wiki/Adenosine_monophosphate" title="Adenosine monophosphate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Adenosine monophosphate">adenosine monophosphate</a>.</p> <h3>Nucleobase classification</h3 style="background-image: none; margin> <p>The nucleobases are classified into two types: 0px 0px 0.3emthe&nbsp; overflow<a href="http: hidden; padding-top: 0//en.5em; padding-bottom: 0wikipedia.17em; border-bottomorg/wiki/Purine" style="text-styledecoration: none; font-sizecolor: 16.799999237060547pxrgb(11, 0, 128); fontbackground-familyimage: sans-serif; line-height: 19.200000762939453pxnone;"><span classtitle="mw-headline" id="Nucleobase_classificationPurine">Nucleobase classificationpurines</spana>, A and G, being fused five- and six-membered&nbsp;</h3><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Heterocyclic_compound" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;"title="Heterocyclic compound">heterocyclic compounds</a>The nucleobases are classified into two types: , and the&nbsp;<a href="http://en.wikipedia.org/wiki/Purine" title="PurinePyrimidine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Pyrimidine">purinespyrimidines</a>, A and G, being fused five- and the six-membered&nbsp;rings C and T.^{<a href="http://en.wikipedia.org/wiki/Heterocyclic_compound" title="Heterocyclic compoundDNA#cite_note-berg-9" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">heterocyclic compounds[9]</a>}&nbsp;A fifth pyrimidine nucleobase, and the&nbsp;<a href="http://en.wikipedia.org/wiki/Pyrimidine" title="PyrimidineUracil" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Uracil">pyrimidinesuracil</a>&nbsp;(U), usually takes the six-membered rings C place of thymine in RNA and T.differs from thymine by lacking a&nbsp;<sup ida href="cite_ref-berg_9-2" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-berg-9Methyl_group" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Methyl group">[9]methyl group</a></sup>&nbsp;A fifth pyrimidine nucleobase,&nbsp;<on its ring. In addition to RNA and DNA a large number of artificial&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Uracil" title="UracilNucleic_acid_analogues" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleic acid analogues">uracilnucleic acid analogues</a>&nbsp;(U), usually takes have also been created to study the place properties of thymine nucleic acids, or for use in RNA and differs from thymine by lacking a&nbsp;biotechnology.^{<a href="http://en.wikipedia.org/wiki/Methyl_group" title="Methyl groupDNA#cite_note-14" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">methyl group[14]</a>&nbsp;on its ring}</p> <p>Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine. In addition to RNA and DNA However in a large number of artificialbacteriophages &ndash;&nbsp;<a href="http:em>Bacillus subtilis</em>&nbsp;bacteriophages PBS1 and PBS2 and&nbsp;<em>Yersinia</en.wikipedia.orgem>&nbsp;bacteriophage piR1-37 &ndash; thymine has been replaced by uracil.^{<a href="http://en.wikipedia.org/wiki/Nucleic_acid_analogues" title="Nucleic acid analogues" class="mwDNA#cite_note-Kiljunen2005-redirect15" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">nucleic acid analogues[15]</a>&nbsp;have also been created to study the properties of nucleic acids, or for use in biotechnology.<sup id/sup></p> <p><a href="cite_ref-14" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://enhttp://en.wikipedia.org/wiki/DNA#cite_note-14Base_J" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Base J">[14]Base J</a>}</p><p style="margin: 0.4em 0px 0.5em&nbsp; line(beta-height: 19.200000762939453px; fontd-family: sans-serif; font-size: 12.800000190734863px;">Uracil glucopyranosyloxymethyluracil), a modified form of uracil, is not usually also found in DNA, occurring only as a breakdown product number of cytosine. However in a number of bacteriophages &ndash;organisms: the flagellates&nbsp;<iem>Bacillus subtilis<a class="new" href="http://i>&nbsp;bacteriophages PBS1 and PBS2 anden.wikipedia.org/w/index.php?title=Diplonema_(protozoa)&nbspamp;<i>Yersinia</i>action=edit&nbspamp;bacteriophage piR1-37 &ndash; thymine has been replaced by uracil.<sup idredlink="cite_ref-Kiljunen2005_15-0" class="reference1" style="linetext-heightdecoration: 1emnone; unicode-bidicolor: -webkit-isolate;"rgb(165, 88, 88); background-image: none;" title="Diplonema (protozoa) (page does not exist)">Diplonema</a href="http:/></enem>&nbsp;and<em><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Kiljunen2005-15Euglena" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Euglena">[15]Euglena</a></supem>, and all the&nbsp;</p><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; line-height: 19.200000762939453pxorg/wiki/Kinetoplastid" style="text-decoration: none; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="Kinetoplastid">kinetoplastid</a href>&nbsp;genera^{<a href="http://en.wikipedia.org/wiki/Base_J" title="Base JDNA#cite_note-Simpson1998-16" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">Base J[16]</a>&}&nbsp;(beta-d-glucopyranosyloxymethyluracil), a modified form Biosynthesis of uracil, is also found J occurs in a number of organismstwo steps: in the flagellates&nbspfirst step a specific thymidine in DNA is converted into hydroxymethyldeoxyuridine;in the second HOMedU is glycosylated to form J.<isup><a href="http://en.wikipedia.org/wwiki/index.php?titleDNA#cite_note-Borst2008-17" style=Diplonema_"text-decoration: none; color: rgb(protozoa11, 0, 128)&amp;action=edit&ampbackground-image: none;redlink=1" classwhite-space: nowrap;">[17]</a></sup>&nbsp;Proteins that bind specifically to this base have been identified.^{<a href="new" title="Diplonema (protozoa) (page does not exist)http://en.wikipedia.org/wiki/DNA#cite_note-Cross1999-18" style="text-decoration: none; color: rgb(16511, 880, 88128); background-image: none; white-space: nowrap;">Diplonema[18]</a></isup>&nbsp;and<isup><a href="http://en.wikipedia.org/wiki/Euglena" title="EuglenaDNA#cite_note-DiPaolo2005-19" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">Euglena[19]</a></isup>^{, and all the&nbsp;<a href="http://en.wikipedia.org/wiki/Kinetoplastid" title="KinetoplastidDNA#cite_note-Vainio2009-20" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">kinetoplastid[20]</a>}&nbsp;These proteins appear to be distant relatives of the Tet1 oncogene that is involved in the pathogenesis of&nbsp;genera<sup id="cite_ref-Simpson1998_16-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a a href="http://en.wikipedia.org/wiki/DNA#cite_note-Simpson1998-16Acute_myeloid_leukemia" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Acute myeloid leukemia">[16]acute myeloid leukemia</a>.}&nbsp;Biosynthesis of J occurs in two steps<a href="http: in the first step a specific thymidine in //en.wikipedia.org/wiki/DNA is converted into hydroxymethyldeoxyuridine#cite_note-Iyer2009-21" style="text-decoration: none; in the second HOMedU is glycosylated to form J.<sup id="cite_ref-Borst2008_17-color: rgb(11, 0" class="reference" style="line, 128); background-heightimage: 1emnone; unicodewhite-bidispace: -webkit-isolatenowrap;">[21]</a></sup>&nbsp;J appears to act as a termination signal for&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-Borst2008-17" RNA_polymerase_II" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="RNA polymerase II">[17]RNA polymerase II</a>.</sup>&nbsp;Proteins that bind specifically to this base have been identified<a href="http://en.wikipedia.<sup id="cite_reforg/wiki/DNA#cite_note-Cross1999_18van_Luenen2012-0" class="reference22" style="linetext-heightdecoration: 1emnone; color: rgb(11, 0, 128); unicodebackground-bidiimage: none; white-webkit-isolatespace: nowrap;">[22]</a></sup>^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-Cross1999Hazelbaker2012-1823" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[1823]</a>}<sup id="cite_ref-DiPaolo2005_19-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-DiPaolo2005-19" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[19]</a></sup><sup id="cite_ref-Vainio2009_20-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Vainio2009-20" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[20]</a></sup>&nbsp;These proteins appear to be distant relatives of the Tet1 oncogene that is involved in the pathogenesis of&nbsp;<a href="http://en.wikipedia.org/wiki/Acute_myeloid_leukemia" title="Acute myeloid leukemia" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">acute myeloid leukemia</a>.<sup id="cite_ref-Iyer2009_21-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Iyer2009-21" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[21]</a></sup>&nbsp;J appears to act as a termination signal for&nbsp;<a href="http://en.wikipedia.org/wiki/RNA_polymerase_II" title="RNA polymerase II" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">RNA polymerase II</a>.<sup id="cite_ref-van_Luenen2012_22-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-van_Luenen2012-22" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[22]</a></sup><sup id="cite_ref-Hazelbaker2012_23-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Hazelbaker2012-23" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[23]</a></sup></p/p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:DNA-ligand-by-Abalone.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8b/DNA-ligand-by-Abalone.png/220px-DNA-ligand-by-Abalone.png" widthstyle="220" height="148" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/DNAbackground-ligand-by-Abalone.png/330px-DNA-ligand-by-Abalone.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/8/8b/DNA-ligand-by-Abalone.png/440px-DNA-ligand-by-Abalone.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:148px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:DNA-ligand-by-Abalone.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>Major and minor grooves of DNA. Minor groove is a binding site for the dye&nbsp;<a href="http://en.wikipedia.org/wiki/Hoechst_stain" title="Hoechst stain" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hoechst stain">Hoechst 33258</a>.</div>

 <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Grooves">Grooves</span></h3> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">Twin helical strands form the DNA backbone. Another double helix may be found tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a&nbsp;<a href="http://en.wikipedia.org/wiki/Binding_site" title="Binding site" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Binding site">binding site</a>. As the strands are not symmetrically located with respect to each other, the grooves are unequally sized. One groove, the major groove, is 22&nbsp;&Aring; wide and the other, the minor groove, is 12&nbsp;&Aring; wide.<sup id="cite_ref-24" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-24" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[24]</a></sup>&nbsp;The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like&nbsp;<a href="http://en.wikipedia.org/wiki/Transcription_factor" title="Transcription factor" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Transcription factor">transcription factors</a>&nbsp;that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove.<sup id="cite_ref-Pabo1984_25-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Pabo1984-25" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[25]</a></sup>&nbsp;This situation varies in unusual conformations of DNA within the cell&nbsp;<iem>(see below)</iem>, but the major and minor grooves are always named to reflect the differences in size that would be seen if the DNA is twisted back into the ordinary B form.</p> <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Base_pairing">Base pairing</span></h3> <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/Base_pair" title="Base pair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Base pair">Base pair</a></div> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called complementary&nbsp;<a href="http://en.wikipedia.org/wiki/Base_pair" title="Base pair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Base pair">base pairing</a>. Here, purines form&nbsp;<a href="http://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydrogen bond">hydrogen bonds</a>&nbsp;to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across the double helix is called a base pair. As hydrogen bonds are not&nbsp;<a href="http://en.wikipedia.org/wiki/Covalent_bond" title="Covalent bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Covalent bond">covalent</a>, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can therefore be pulled apart like a zipper, either by a mechanical force or high&nbsp;<a href="http://en.wikipedia.org/wiki/Temperature" title="Temperature" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Temperature">temperature</a>.<sup id="cite_ref-26" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-26" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[26]</a></sup>&nbsp;As a result of this complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. Indeed, this reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms.<sup id="cite_ref-Alberts_3-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Alberts-3" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[3]</a></sup></p> 

<table border="0" cellpadding="2" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 230px; margin: 0.3em;width:230px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:GC_DNA_base_pair.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="GC DNA base pair.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/GC_DNA_base_pair.svg/282px-GC_DNA_base_pair.svg.png" width="282" height="177" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d7/GC_DNA_base_pair.svg/423px-GC_DNA_base_pair.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d7/GC_DNA_base_pair.svg/564px-GC_DNA_base_pair.svg.png 2x" style="border: none; height:177px; vertical-align: middle;width:282px" /></a></td> </tr> </tbody>

 <table border="0" cellpadding="2" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 230px; margin: 0.3em;width:230px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:AT_DNA_base_pair.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="AT DNA base pair.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/AT_DNA_base_pair.svg/282px-AT_DNA_base_pair.svg.png" width="282" height="151" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/91/AT_DNA_base_pair.svg/423px-AT_DNA_base_pair.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/91/AT_DNA_base_pair.svg/564px-AT_DNA_base_pair.svg.png 2x" style="border: none; height:151px; vertical-align: middle;width:282px" /></a></td> </tr> </tbody>

<div class="thumbcaption" style="border: none; line-height: 1.4em; font-size: 12px; padding: 3px !important;">Top, a&nbsp;<bstrong>GC</bstrong>&nbsp;base pair with three&nbsp;<a href="http://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydrogen bond">hydrogen bonds</a>. Bottom, an&nbsp;<bstrong>AT</bstrong>&nbsp;base pair with two hydrogen bonds. Non-covalent hydrogen bonds between the pairs are shown as dashed lines.</div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, right). DNA with high&nbsp;<a href="http://en.wikipedia.org/wiki/GC-content" title="GC-content" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="GC-content">GC-content</a>&nbsp;is more stable than DNA with low GC-content.</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">As noted above, most DNA molecules are actually two >As noted above, most DNA molecules are actually two polymer strands, bound together in a helical fashion by noncovalent bonds; this double stranded structure (<bstrong>dsDNA</bstrong>) is maintained largely by the intrastrand base stacking interactions, which are strongest for G,C stacks. The two strands can come apart&nbsp;&ndash; a process known as melting&nbsp;&ndash; to form two single-stranded DNA molecules (<bstrong>ssDNA</bstrong>) molecules. Melting occurs at high temperature, low salt and high pH (low pH also melts DNA, but since DNA is unstable due to acid depurination, low pH is rarely used).</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">>The stability of the dsDNA form depends not only on the GC-content (% G,C basepairs) but also on sequence (since stacking is sequence specific) and also length (longer molecules are more stable). The stability can be measured in various ways; a common way is the &quot;melting temperature&quot;, which is the temperature at which 50% of the ds molecules are converted to ss molecules; melting temperature is dependent on ionic strength and the concentration of DNA. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determines the strength of the association between the two strands of DNA. Long DNA helices with a high GC-content have stronger-interacting strands, while short helices with high AT content have weaker-interacting strands.<sup id="cite_ref-27" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">><a href="http://en.wikipedia.org/wiki/DNA#cite_note-27" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[27]</a></sup>&nbsp;In biology, parts of the DNA double helix that need to separate easily, such as the TATAAT&nbsp;<a href="http://en.wikipedia.org/wiki/Pribnow_box" title="Pribnow box" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Pribnow box">Pribnow box</a>&nbsp;in some&nbsp;<a hrefclass="mw-redirect" href="http://en.wikipedia.org/wiki/Promoter_(biology)" title="Promoter (biology)" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Promoter (biology)">promoters</a>, tend to have a high AT content, making the strands easier to pull apart.<sup id><a href="cite_ref-28" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:http://en.wikipedia.org/wiki/DNA#cite_note-28" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[28]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In the laboratory, >In the laboratory, the strength of this interaction can be measured by finding the temperature necessary to break the hydrogen bonds, their&nbsp;<a hrefclass="mw-redirect" href="http://en.wikipedia.org/wiki/DNA_melting" title="DNA melting" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA melting">melting temperature</a>&nbsp;(also called&nbsp;<iem>T<sub style="line-height: 1em;">m</sub></iem>&nbsp;value). When all the base pairs in a DNA double helix melt, the strands separate and exist in solution as two entirely independent molecules. These&nbsp;single-stranded DNA molecules (<iem>ssDNA</iem>) have no single common shape, but some conformations are more stable than others.<sup id="cite_ref-29" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-29" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[29]</a></sup></p> <h3 style="background-image>Sense and antisense</h3> <div class="rellink boilerplate further" style="font-style: none; margin: 0px 0px 0.3em; overflow: hiddenitalic; padding-topleft: 01.5em6em; paddingmargin-bottom: 0.17em5em; borderfont-bottomfamily: sans-style: noneserif; font-size: 1612.799999237060547px; font-family: sans-serif800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<span classa href="mw-headline" id="Sense_and_antisense">Sense and antisense<http:/span></h3><div class="rellink boilerplate furtheren.wikipedia.org/wiki/Sense_(molecular_biology)" style="fonttext-styledecoration: italicnone; padding-left: 1.6em; margin-bottomcolor: rgb(11, 0.5em, 128); fontbackground-familyimage: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453pxnone;">Further information:&nbsp;<a hreftitle="http://en.wikipedia.org/wiki/Sense_Sense (molecular_biologymolecular biology)" title=">Sense (molecular biology)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Sense (molecular biology)</a</a></div> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">A >A DNA sequence is called &quot;sense&quot; if its sequence is the same as that of a&nbsp;<a href="http://en.wikipedia.org/wiki/Messenger_RNA" title="Messenger RNA" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Messenger RNA">messenger RNA</a>&nbsp;copy that is translated into protein.<sup id="cite_ref-30" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-30" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[30]</a></sup>&nbsp;The sequence on the opposite strand is called the &quot;antisense&quot; sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear.<sup id="cite_ref-31" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">><a href="http://en.wikipedia.org/wiki/DNA#cite_note-31" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[31]</a></sup>&nbsp;One proposal is that antisense RNAs are involved in regulating&nbsp;<a href="http://en.wikipedia.org/wiki/Gene_expression" title="Gene expression" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Gene expression">gene expression</a>&nbsp;through RNA-RNA base pairing.<sup id="cite_ref-32" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><><a href="http://en.wikipedia.org/wiki/DNA#cite_note-32" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[32]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">A few DNA sequences in prokaryotes >A few DNA sequences in prokaryotes and eukaryotes, and more in&nbsp;<a href="http://en.wikipedia.org/wiki/Plasmid" title="Plasmid" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Plasmid">plasmids</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Virus" title="Virus" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Virus">viruses</a>, blur the distinction between sense and antisense strands by having&nbsp;<a href="http://en.wikipedia.org/wiki/Overlapping_gene" title="Overlapping gene" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Overlapping gene">overlapping genes</a>.<sup id><a href="cite_ref-33" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-33" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[33]</a></sup>&nbsp;In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. In&nbsp;<a href="http://en.wikipedia.org/wiki/Bacteria" title="Bacteria" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bacteria">bacteria</a>, this overlap may be involved in the regulation of gene transcription,<sup id="cite_ref-34" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-34" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[34]</a></sup>&nbsp;while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome.<sup id><a href="cite_ref-35" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-35" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[35]</a></sup></p> <h3 style="background>Supercoiling</h3> <div class="rellink boilerplate further" style="font-imagestyle: none; margin: 0px 0px 0.3em; overflow: hiddenitalic; padding-topleft: 01.5em6em; paddingmargin-bottom: 0.17em5em; borderfont-bottomfamily: sans-style: noneserif; font-size: 1612.799999237060547px; font-family: sans-serif800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<span classa href="mw-headline" id="Supercoiling">Supercoiling<http://span><en.wikipedia.org/wiki/h3><div class="rellink boilerplate furtherDNA_supercoil" style="fonttext-styledecoration: italicnone; padding-left: 1.6em; margin-bottomcolor: rgb(11, 0.5em, 128); fontbackground-familyimage: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453pxnone;">Further information:title="DNA supercoil">DNA supercoil</a></div> <p>DNA can be twisted like a rope in a process called&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_supercoil" titlestyle="DNA supercoil" style="text-text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA supercoil">DNA supercoilsupercoiling</a></div><p style="margin: 0.4em 0px 0.5emWith DNA in its &quot; line-height: 19.200000762939453pxrelaxed&quot; font-family: sans-serif; font-size: 12.800000190734863px;">DNA can be twisted like state, a rope in a process called&nbsp;<a href="http://enstrand usually circles the axis of the double helix once every 10.wikipedia.org4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound.^{<a href="http://en.wikipedia.org/wiki/DNA_supercoil" title="DNA supercoil#cite_note-36" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">DNA supercoiling[36]</a>. With DNA in its}&quotnbsp;relaxed&quot; state, a strand usually circles If the axis of DNA is twisted in the direction of the double helix once every 10.4 base pairs, but if the DNA this is twisted positive supercoiling, and the strands become bases are held more tightly or more loosely woundtogether.<sup id="cite_ref-36" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolateIf they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that is introduced by&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-36Enzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Enzyme">[36]<enzymes</a></sup>&nbsp;If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly togethercalled&nbsp;<a href="http://en.wikipedia. If they are twisted in the opposite directionorg/wiki/Topoisomerase" style="text-decoration: none; color: rgb(11, this is negative supercoiling0, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that is introduced by&nbsp128); background-image: none;<" title="Topoisomerase">topoisomerases</a>.^{<a href="http://en.wikipedia.org/wiki/Enzyme" title="EnzymeDNA#cite_note-Champoux-37" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">enzymes[37]</a>}&nbsp;calledThese enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as&nbsp;<a href="http://en.wikipedia.org/wiki/Topoisomerase" title="TopoisomeraseTranscription_(genetics)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">topoisomerasestitle="Transcription (genetics)">transcription</a>.&nbsp;and&nbsp;<sup ida href="cite_ref-Champoux_37-0http://en.wikipedia.org/wiki/DNA_replication" classstyle="reference" style="linetext-heightdecoration: none; color: 1emrgb(11, 0, 128); unicodebackground-bidiimage: -webkit-isolatenone;" title="DNA replication">DNA replication</a href=">.^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-ChampouxWang-3738" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[37]</a>}&nbsp;These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as&nbsp;<a href="http://en.wikipedia.org/wiki/Transcription_(genetics)" title="Transcription (genetics)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">transcription</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_replication" title="DNA replication" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA replication</a>.<sup id="cite_ref-Wang_38-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Wang-38" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[3838]</a></sup></p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:A-DNA,_B-DNA_and_Z-DNA.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/A-DNA%2C_B-DNA_and_Z-DNA.png/220px-A-DNA%2C_B-DNA_and_Z-DNA.png" widthstyle="220" height="143" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Abackground-DNA%2C_B-DNA_and_Z-DNA.png/330px-A-DNA%2C_B-DNA_and_Z-DNA.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/b/b1/A-DNA%2C_B-DNA_and_Z-DNA.png/440px-A-DNA%2C_B-DNA_and_Z-DNA.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:143px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:A-DNA,_B-DNA_and_Z-DNA.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>

 <h3>Alternate DNA structures</h3 > <div class="rellink boilerplate further" style="backgroundfont-imagestyle: none; margin: 0px 0px 0.3em; overflow: hiddenitalic; padding-topleft: 01.5em6em; paddingmargin-bottom: 0.17em5em; borderfont-bottomfamily: sans-style: noneserif; font-size: 1612.799999237060547px; font-family: sans-serif800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<span classa href="mw-headlinehttp://en.wikipedia.org/wiki/Molecular_Structure_of_Nucleic_Acids:_A_Structure_for_Deoxyribose_Nucleic_Acid" idstyle="Alternate_DNA_structures">Alternate DNA structures</span></h3><div class="rellink boilerplate further" style="font-styletext-decoration: none; color: italicrgb(11, 0, 128); paddingbackground-leftimage: 1.6emnone; margin-bottom" title="Molecular Structure of Nucleic Acids: 0.5em; font-familyA Structure for Deoxyribose Nucleic Acid">Molecular Structure of Nucleic Acids: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;"A Structure for Deoxyribose Nucleic Acid</a>Further information:,&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_Structure_of_Nucleic_Acids:_A_Structure_for_Deoxyribose_Nucleic_Acid" title="Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic AcidMolecular_models_of_DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Molecular models of DNA">Molecular Structure models of Nucleic Acids: A Structure for Deoxyribose Nucleic AcidDNA</a>,&nbsp;and<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Molecular_models_of_DNA" title="Molecular models of DNADNA_structure" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Molecular models of title="DNA structure">DNAstructure</a>, and</div> <p>DNA exists in many possible&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_structure" title="DNA structure" class="mw-redirectConformational_isomerism" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA structuretitle="Conformational isomerism">conformations</a>&nbsp;that include&nbsp;</div><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/A-height: 19.200000762939453pxDNA" style="text-decoration: none; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="A-DNA">A-DNA exists in many possible</a>, B-DNA, and&nbsp;<a href="http://en.wikipedia.org/wiki/Conformational_isomerism" title="Conformational isomerismZ-DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Z-DNA">conformationsZ-DNA</a>&nbsp;that include&nbsp;<forms, although, only B-DNA and Z-DNA have been directly observed in functional organisms.^{<a href="http://en.wikipedia.org/wiki/ADNA#cite_note-DNA" title="AGhosh-DNA11" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">A-DNA[11]</a>, B-}&nbsp;The conformation that DNA adopts depends on the hydration level, DNAsequence, the amount anddirection of supercoiling, chemical modifications of the bases, the type and concentration of metal&nbsp;<a href="http://en.wikipedia.org/wiki/Z-DNAIon" titlestyle="Z-DNA" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ion">Z-DNAions</a>&nbsp;forms, although, only B-DNA and Z-DNA have been directly observed in functional organisms.<sup id="cite_ref-Ghosh_11-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">as well as the presence of<a href="http://en.wikipedia.org/wiki/DNA#cite_note-Ghosh-11Polyamine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[11]title="Polyamine">polyamines</a>&nbsp;in solution.</sup>&nbsp;The conformation that <a href="http://en.wikipedia.org/wiki/DNA adopts depends on the hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal&nbsp;<a href#cite_note-39" style="httptext-decoration: none; color://en.wikipedia.org/wiki/Ion" title="Ion" style="text-decoration: none; color: rgb(rgb(11, 0, 128); background-image: none; white-space: nowrap;">ions[39]</a>, as well as the presence of</sup></p> <p>The first published reports of A-DNA&nbsp;<a href="http://en.wikipedia.org/wiki/Polyamine" title="PolyamineX-ray_scattering_techniques" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="X-ray scattering techniques">polyaminesX-ray diffraction patterns</a>&nbsp;in solution.<sup id="cite_ref&mdash; and also B-39" class="reference" style="line-height: 1emDNA &mdash; unicode-bidi: -webkit-isolateused analyses based on&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-39Patterson_function" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Patterson function">[39]Patterson transforms</a>&nbsp;that provided only a limited amount of structural information for oriented fibers of DNA.</sup></p><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/DNA#cite_note-40" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); background-image: none; fontwhite-sizespace: 12.800000190734863pxnowrap;">The first published reports of A-DNA&nbsp;[40]</a></sup>^{<a href="http://en.wikipedia.org/wiki/XDNA#cite_note-ray_scattering_techniques" title="XNatFranGos-ray scattering techniques41" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">X-ray diffraction patterns[41]</a>}&nbsp;An alternate analysis was then proposed by Wilkins<em>et al.</em>, in 1953, for the&mdash; and also B-DNA &mdashnbsp; used analyses based on<em>in vivo</em>&nbsp;<a href="http:B-DNA X-ray diffraction/scattering patterns of highly hydrated DNA fibers in terms of squares of&nbsp;<a href="http://en.wikipedia.org/wiki/Patterson_function" title="Patterson functionBessel_function" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bessel function">Patterson transformsBessel functions</a>&nbsp;that provided only a limited amount of structural information for oriented fibers of DNA.<.<sup id="cite_ref-40" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-40NatWilk-42" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4042]</a></sup><sup id="cite_ref-NatFranGos_41-0" class="reference" style="line-height: 1em&nbsp; unicode-bidi: -webkit-isolateIn the same journal,&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-NatFranGos-41James_Watson" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="James Watson">[41]James Watson</a></sup>&nbsp;An alternate analysis was then proposed by Wilkins<i>et al.</i>, in 1953, for theand&nbsp;<i>in vivo</i>&nbsp;B-DNA X-ray diffraction/scattering patterns of highly hydrated DNA fibers in terms of squares of&nbsp;<a hrefa href="http://en.wikipedia.org/wiki/Bessel_function" title="Bessel functionFrancis_Crick" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Bessel functionstitle="Francis Crick">Francis Crick</a>.<sup id="cite_ref-NatWilk_42-0" class="reference" style="line-height: 1em&nbsp; unicode-bidi: -webkit-isolatepresented their&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-NatWilk-42" Molecular_models_of_DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Molecular models of DNA">[42]molecular modeling</a></sup>&nbsp;In analysis of the same journal,&nbsp;DNA X-ray diffraction patterns to suggest that the structure was a double-helix.^{<a href="http://en.wikipedia.org/wiki/James_Watson" title="James WatsonDNA#cite_note-FWPUB-5" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">James Watson[5]</a>&nbsp;and&nbsp;}</p> <p>Although the &quot;B-DNA form&quot; is most common under the conditions found in cells,^{<a href="http://en.wikipedia.org/wiki/Francis_CrickDNA#cite_note-43" title="Francis Crick" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">Francis Crick[43]</a>}&nbsp;presented their&nbsp;it is not a well-defined conformation but a family of related DNA conformations^{<a href="http://en.wikipedia.org/wiki/Molecular_models_of_DNA" title="Molecular models of DNA#cite_note-44" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">molecular modeling[44]</a>}&nbsp;analysis of that occur at the DNA high hydration levels present in living cells. Their corresponding X-ray diffraction and scattering patterns to suggest that the structure was a double-helix.<sup id="cite_ref-FWPUB_5-1" class="reference" style="line-height: 1emare characteristic of molecular&nbsp; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-FWPUB-5Paracrystalline" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Paracrystalline">[5]paracrystals</a>&nbsp;with a significant degree of disorder.</sup></p><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/DNA#cite_note-45" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: none; white-space: 12.800000190734863pxnowrap;">Although the &quot;B-DNA form&quot; is most common under the conditions found in cells,[45]</a></sup><sup id="cite_ref-43" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-4346" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4346]</a></sup>&nbsp;it is not a well-defined conformation but a family of related DNA conformations<sup id="cite_ref/p> <p>Compared to B-44" class="reference" style="lineDNA, the A-height: 1em; unicodeDNA form is a wider right-bidi: -webkit-isolate;"><handed spiral, with a shallow, wide minor groove and a href="http://ennarrower, deeper major groove.wikipedia.org/wiki/DNA#cite_noteThe A form occurs under non-44" stylephysiological conditions in partially dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, as well as in enzyme-DNA complexes.^{<a href="text-decoration: none; colorhttp://en.wikipedia.org/wiki/DNA#cite_note-47" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4447]</a>}&nbsp;that occur at the high hydration levels present in living cells. Their corresponding X-ray diffraction and scattering patterns are characteristic of molecular&nbsp;<a href="http^{<a href="http://en.wikipedia.org/wiki/Paracrystalline" title="ParacrystallineDNA#cite_note-48" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">paracrystalswhite-space: nowrap;">[48]</a>}Segments of DNA where the bases have been chemically modified by&nbsp;with <a significant degree of disorder.<sup idhref="cite_ref-45" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-45Methylation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Methylation">[45]methylation</a>&nbsp;may undergo a larger change in conformation and adopt the&nbsp;</sup><sup ida href="cite_refhttp://en.wikipedia.org/wiki/Z-46DNA" classstyle="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-46" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none; white" title="Z-space: nowrap;DNA">[46]Z form</a>. Here, the strands turn about the helical axis in a&nbsp;</sup></p><p stylea class="marginmw-redirect" href="http: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Left-height: 19.200000762939453px; fonthanded" style="text-familydecoration: sans-serifnone; font-sizecolor: 12.800000190734863pxrgb(11, 0, 128); background-image: none;" title="Left-handed">Compared to Bleft-DNAhanded</a>&nbsp;spiral, the A-DNA opposite of the more common B form is .^{<a wider righthref="http://en.wikipedia.org/wiki/DNA#cite_note-49" style="text-handed spiraldecoration: none; color: rgb(11, with a shallow0, wide minor groove and a narrower, deeper major groove. The A form occurs under non128); background-image: none; white-space: nowrap;">[49]</a>}&nbsp;These unusual structures can be recognized by specific Z-physiological conditions in partially dehydrated samples of DNA, while in the cell it binding proteins and may be produced involved in hybrid pairings the regulation of DNA and RNA strands, as well as in enzyme-DNA complexes.<sup id="cite_ref-47" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"transcription.^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-4750" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4750]</a>}<sup id="cite_ref-48" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"/p> <h3>Alternate DNA chemistry</h3> <p>For a href="http://ennumber of years exobiologists have proposed the existence of a&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-48Shadow_biosphere" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Shadow biosphere">[48]shadow biosphere</a></sup>Segments , a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. One of DNA where the bases have been chemically modified byproposals was the existence of lifeforms that use&nbsp;<a hrefclass="mw-redirect" href="http://en.wikipedia.org/wiki/Methylation" title="MethylationArsenic_DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Arsenic DNA">methylationarsenic instead of phosphorus in DNA</a>. A report in 2010 of the possibility in the&nbsp;may undergo a larger change in conformation and adopt the&nbsp;<<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Z-DNA" title="Z-DNABacterium" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bacterium">Z formbacterium</a>. Here, the strands turn about the helical axis in a&nbsp;<a href="http://en.wikipedia.org/wiki/LeftGFAJ-handed" title="Left-handed" class="mw-redirect1" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="GFAJ-1">leftGFAJ-handed1</a>&nbsp;spiral, the opposite of the more common B form.was announced,<sup id="cite_ref-49" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-49arsenic_extremophile-51" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[4951]</a></sup>&nbsp;These unusual structures can be recognized by specific Z^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-DNA binding proteins and may be involved in the regulation of transcription.<sup id="cite_refarsenic_extremophile-50" class="reference51" style="linetext-heightdecoration: 1emnone; unicodecolor: rgb(11, 0, 128); background-bidiimage: none; white-webkit-isolatespace: nowrap;">[51]</a>}^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-50Space-52" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5052]</a>}</p&nbsp;though the research was disputed,^{<h3 a href="http://en.wikipedia.org/wiki/DNA#cite_note-Space-52" style="backgroundtext-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflow: hidden; paddingbackground-top: 0.5em; padding-bottom: 0.17em; border-bottom-styleimage: none; fontwhite-sizespace: 16.799999237060547pxnowrap; font-family: sans-serif; line-height: 19.200000762939453px;"">[52]</a><span class="mw-headline" id="Alternate_DNA_chemistry">Alternate DNA chemistry</spansup></h3sup><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/DNA#cite_note-53" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone; white-space: nowrap;">For a number of years exobiologists have proposed the existence of [53]</a>}&nbsp;<a href="http:/and evidence suggests the bacterium actively prevents the incorporation of arsenic into the DNA backbone and other biomolecules.^{<a href="http://en.wikipedia.org/wiki/Shadow_biosphere" title="Shadow biosphereDNA#cite_note-Nature-54" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">shadow biosphere[54]</a>, a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. One of the proposals was the existence of lifeforms that use&nbsp;<a href="http:/sup></en.wikipedia.orgp> <h3>Quadruplex structures</wiki/Arsenic_DNA" title="Arsenic DNA" h3> <div class="mw-redirectrellink boilerplate further" style="textfont-decorationstyle: noneitalic; colorpadding-left: 1.6em; margin-bottom: rgb(11, 0, 128).5em; font-family: sans-serif; font-size: 12.800000190734863px; backgroundline-imageheight: none19.200000762939453px;">arsenic instead of phosphorus in DNA</a>. A report in 2010 of the possibility in theFurther information:&nbsp;<a href="http://en.wikipedia.org/wiki/Bacterium" title="Bacterium" class="mwG-redirectquadruplex" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="G-quadruplex">bacteriumG-quadruplex</a></div> <p>At the ends of the linear chromosomes are specialized regions of DNA called&nbsp;<a href="http://en.wikipedia.org/wiki/GFAJ-1" title="GFAJ-1Telomere" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Telomere">GFAJ-1telomeres</a>, was announced,. The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme&nbsp;<sup ida href="cite_ref-arsenic_extremophile_51-0http://en.wikipedia.org/wiki/Telomerase" classstyle="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-arsenic_extremophile-51" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Telomerase">[51]telomerase</a>, as the enzymes that normally replicate DNA cannot copy the extreme 3&prime; ends of chromosomes.}<sup ida href="cite_ref-arsenic_extremophile_51-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-arsenic_extremophileGreider-5155" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5155]</a></sup><sup id="cite_ref-Space_52-0" class="reference" style="line-height: 1em&nbsp;These specialized chromosome caps also help protect the DNA ends, and stop the&nbsp; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Space-52DNA_repair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="DNA repair">[52]DNA repair</a></sup>&nbsp;though systems in the research was disputed,cell from treating them as damage to be corrected.<sup id><a href="cite_ref-Space_52-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-SpaceNugent-5256" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5256]</a></sup>&nbsp;In&nbsp;<sup ida href="cite_ref-53" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-53List_of_distinct_cell_types_in_the_adult_human_body" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[53]title="List of distinct cell types in the adult human body">human cells</a>, telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence.</sup>&nbsp;and evidence suggests the bacterium actively prevents the incorporation of arsenic into the <a href="http://en.wikipedia.org/wiki/DNA backbone and other biomolecules.<sup id="cite_ref#cite_note-Nature_54-0" class="reference57" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Nature-54" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5457]</a></sup></p><h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Quadruplex_structures">Quadruplex structures</span></h3><div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/G-quadruplex" title="G-quadruplex" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">G-quadruplex</a></div><p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">At the ends of the linear chromosomes are specialized regions of DNA called&nbsp;<a href="http://en.wikipedia.org/wiki/Telomere" title="Telomere" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">telomeres</a>. The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme&nbsp;<a href="http://en.wikipedia.org/wiki/Telomerase" title="Telomerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">telomerase</a>, as the enzymes that normally replicate DNA cannot copy the extreme 3&prime; ends of chromosomes.<sup id="cite_ref-Greider_55-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Greider-55" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[55]</a></sup>&nbsp;These specialized chromosome caps also help protect the DNA ends, and stop the&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_repair" title="DNA repair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA repair</a>&nbsp;systems in the cell from treating them as damage to be corrected.<sup id="cite_ref-Nugent_56-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Nugent-56" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[56]</a></sup>&nbsp;In&nbsp;<a href="http://en.wikipedia.org/wiki/List_of_distinct_cell_types_in_the_adult_human_body" title="List of distinct cell types in the adult human body" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">human cells</a>, telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence.<sup id="cite_ref-57" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-57" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[57]</a></sup></p>

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:Parallel_telomere_quadruple.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Parallel_telomere_quadruple.png/220px-Parallel_telomere_quadruple.png" widthstyle="220" height="201" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Parallel_telomere_quadruple.png/330pxbackground-Parallel_telomere_quadruple.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Parallel_telomere_quadruple.png/440px-Parallel_telomere_quadruple.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:201px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:Parallel_telomere_quadruple.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>DNA quadruplex formed by&nbsp;<a href="http://en.wikipedia.org/wiki/Telomere" title="Telomere" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Telomere">telomere</a>repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix.<sup id="cite_ref-58" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-58" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[58]</a></sup></div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">These guanine-rich sequences may stabilize chromosome ends by forming structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases form a flat plate and these flat four-base units then stack on top of each other, to form a stable&nbsp;<a href="http://en.wikipedia.org/wiki/G-quadruplex" title="G-quadruplex" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="G-quadruplex">G-quadruplex</a>&nbsp;structure.<sup id="cite_ref-Burge_59-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Burge-59" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[59]</a></sup>&nbsp;These structures are stabilized by hydrogen bonding between the edges of the bases and&nbsp;<a href="http://en.wikipedia.org/wiki/Chelation" title="Chelation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chelation">chelation</a>&nbsp;of a metal ion in the centre of each four-base unit.<sup id="cite_ref-60" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-60" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[60]</a></sup>&nbsp;Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure.</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here, the single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins.<sup id="cite_ref-61" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-61" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[61]</a></sup>&nbsp;At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This&nbsp;<a href="http://en.wikipedia.org/wiki/Triple-stranded_DNA" title="Triple-stranded DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Triple-stranded DNA">triple-stranded</a>&nbsp;structure is called a displacement loop or&nbsp;<a href="http://en.wikipedia.org/wiki/D-loop" title="D-loop" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="D-loop">D-loop</a>.<sup id="cite_ref-Burge_59-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Burge-59" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[59]</a></sup></p> 

<table border="0" cellpadding="2" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 200px; margin: 0.3em;width:200px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Branch-dna-single.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Branch-dna-single.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/54/Branch-dna-single.svg/95px-Branch-dna-single.svg.png" width="95" height="71" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/54/Branch-dna-single.svg/143px-Branch-dna-single.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/54/Branch-dna-single.svg/190px-Branch-dna-single.svg.png 2x" style="border: none; height:71px; vertical-align: middle;width:95px" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Branch-DNA-multiple.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Branch-DNA-multiple.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Branch-DNA-multiple.svg/95px-Branch-DNA-multiple.svg.png" width="95" height="71" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Branch-DNA-multiple.svg/143px-Branch-DNA-multiple.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/08/Branch-DNA-multiple.svg/190px-Branch-DNA-multiple.svg.png 2x" style="border: none; height:71px; vertical-align: middle;width:95px" /></a></td> </tr> <tr> <td align="center">Single branch</td> <td align="center">Multiple branches</td> </tr> </tbody>

<div class="thumbcaption" style="border: none; line-height: 1.4em; padding: 3px !important;"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Branched_DNA" title="Branched DNA" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Branched DNA">Branched DNA</a>&nbsp;can form networks containing multiple branches.</div>

 <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Branched_DNA">Branched DNA</span></h3> <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Branched_DNA" title="Branched DNA" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Branched DNA">Branched DNA</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_nanotechnology" title="DNA nanotechnology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA nanotechnology">DNA nanotechnology</a></div> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In DNA&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/DNA_end#Frayed_ends" title="DNA end" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA end">fraying</a>&nbsp;occurs when non-complementary regions exist at the end of an otherwise complementary double-strand of DNA. However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible.<sup id="cite_ref-62" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-62" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[62]</a></sup>&nbsp;Branched DNA can be used in&nbsp;<a href="http://en.wikipedia.org/wiki/Nanotechnology" title="Nanotechnology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nanotechnology">nanotechnology</a>&nbsp;to construct geometric shapes, see the section on&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#Uses_in_technology" title="DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA">uses in technology</a>&nbsp;below.</p> <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Vibration">Vibration</span></h3> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">DNA may carry out&nbsp;<a href="http://en.wikipedia.org/wiki/Low-frequency_collective_motion_in_proteins_and_DNA" title="Low-frequency collective motion in proteins and DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Low-frequency collective motion in proteins and DNA">low-frequency</a>&nbsp;collective motion as observed by the&nbsp;<a href="http://en.wikipedia.org/wiki/Raman_spectroscopy" title="Raman spectroscopy" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Raman spectroscopy">Raman spectroscopy</a><sup id="cite_ref-pmid7115900_63-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-pmid7115900-63" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[63]</a></sup><sup id="cite_ref-Urabe_1983_64-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Urabe_1983-64" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[64]</a></sup>&nbsp;and analyzed with a quasi-continuum model.<sup id="cite_ref-pmid6466317_65-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-pmid6466317-65" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[65]</a></sup><sup id="cite_ref-pmid2775828_66-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-pmid2775828-66" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[66]</a></sup></p> <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Chemical_modifications_and_altered_DNA_packaging">Chemical modifications and altered DNA packaging</span></h2> 

<table border="0" cellpadding="2" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 300px; margin: 0.3em;width:300px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Cytosin.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Cytosin.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Cytosin.svg/75px-Cytosin.svg.png" width="75" height="102" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Cytosin.svg/113px-Cytosin.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Cytosin.svg/150px-Cytosin.svg.png 2x" style="border: none; height:102px; vertical-align: middle;width:75px" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:5-Methylcytosine.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="5-Methylcytosine.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/5-Methylcytosine.svg/95px-5-Methylcytosine.svg.png" width="95" height="83" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3a/5-Methylcytosine.svg/143px-5-Methylcytosine.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3a/5-Methylcytosine.svg/190px-5-Methylcytosine.svg.png 2x" style="border: none; height:83px; vertical-align: middle;width:95px" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Thymin.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Thymin.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/15/Thymin.svg/97px-Thymin.svg.png" width="97" height="83" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/15/Thymin.svg/146px-Thymin.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/15/Thymin.svg/194px-Thymin.svg.png 2x" style="border: none; height:83px; vertical-align: middle;width:97px" /></a></td> </tr> <tr> <td align="center"><a href="http://en.wikipedia.org/wiki/Cytosine" title="Cytosine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cytosine">cytosine</a></td> <td align="center"><a href="http://en.wikipedia.org/wiki/5-Methylcytosine" title="5-Methylcytosine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="5-Methylcytosine">5-methylcytosine</a></td> <td align="center"><a href="http://en.wikipedia.org/wiki/Thymine" title="Thymine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Thymine">thymine</a></td> </tr> </tbody>

<div class="thumbcaption" style="border: none; line-height: 1.4em; padding: 3px !important;">Structure of cytosine with and without the 5-methyl group.&nbsp;<a href="http://en.wikipedia.org/wiki/Deamination" title="Deamination" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Deamination">Deamination</a>&nbsp;converts 5-methylcytosine into thymine.</div>

 <h3 >Base modifications and DNA packaging</h3> <div class="rellink boilerplate further" style="backgroundfont-imagestyle: noneitalic; marginpadding-left: 0px 0px 01.3em6em; overflow: hidden; paddingmargin-topbottom: 0.5em; paddingfont-bottomfamily: 0.17em; bordersans-bottom-style: noneserif; font-size: 1612.799999237060547px; font-family: sans-serif800000190734863px; line-height: 19.200000762939453px;"><span classFurther information:&nbsp;<a href="mw-headlinehttp://en.wikipedia.org/wiki/DNA_methylation" idstyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Base_modifications_and_DNA_packaging">Base modifications and DNA packaging</spanmethylation">DNA methylation</h3a>,&nbsp;<div classa href="rellink boilerplate furtherhttp://en.wikipedia.org/wiki/Chromatin_remodeling" style="fonttext-styledecoration: italicnone; padding-left: 1.6em; margin-bottomcolor: rgb(11, 0.5em, 128); fontbackground-familyimage: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453pxnone;" title="Chromatin remodeling">Further information:&nbsp;Chromatin remodeling</a href="http:><//en.wikipedia.org/wiki/DNA_methylation" title="div> <p>The expression of genes is influenced by how the DNA methylation" is packaged in chromosomes, in a structure called&nbsp;<a href="http://en.wikipedia.org/wiki/Chromatin" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA methylationtitle="Chromatin">chromatin</a>. Base modifications can be involved in packaging,&nbsp;with regions that have low or no gene expression usually containing high levels of<a href="http://en.wikipedia.org/wiki/Chromatin_remodeling" title="Chromatin remodelingMethylation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Methylation">Chromatin remodelingmethylation</a>&nbsp;of&nbsp;</div><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Cytosine" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;"title="Cytosine">cytosine</a>The expression of genes is influenced by how &nbsp;bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the DNA is packaged in chromosomes, in a structure called&nbsp;<a href="http://en.wikipedia.org/wiki/ChromatinHistone" title="Chromatin" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Histone">chromatinhistone</a>. Base modifications can be involved &nbsp;protein core around which DNA is wrapped in packaging, with regions that have low the chromatin structure or no gene expression usually containing high levels ofelse by remodeling carried out by chromatin remodeling complexes (see&nbsp;<a href="http://en.wikipedia.org/wiki/MethylationChromatin_remodeling" titlestyle="Methylation" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chromatin remodeling">methylationChromatin remodeling</a>&nbsp;of). There is, further,&nbsp;<a href="http://en.wikipedia.org/wiki/CytosineCrosstalk_(biology)" titlestyle="Cytosine" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Crosstalk (biology)">cytosinecrosstalk</a>&nbsp;bases. between DNA packaging methylation and its influence on gene expression histone modification, so they can also occur by covalent modifications of the&nbsp;coordinately affect chromatin and gene expression.^{<a href="http://en.wikipedia.org/wiki/Histone" title="HistoneDNA#cite_note-67" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">histonewhite-space: nowrap;">[67]</a>}</p> <p>For one example, cytosine methylation, produces&nbsp;protein core around which DNA is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see&nbsp;<<a href="http://en.wikipedia.org/wiki/Chromatin_remodeling5-Methylcytosine" titlestyle="Chromatin remodeling" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="5-Methylcytosine">Chromatin remodeling5-methylcytosine</a>). There , which is, further,important for&nbsp;<a href="http://en.wikipedia.org/wiki/Crosstalk_(biology)" title="Crosstalk (biology)X-inactivation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="X-inactivation">crosstalkX-chromosome inactivation</a>&nbsp;between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression.<sup id.^{<a href="cite_ref-67" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-6768" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[6768]</a>}</p><p style&nbsp;The average level of methylation varies between organisms&nbsp;&ndash; the worm&nbsp;<em><a href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Caenorhabditis_elegans" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;"title="Caenorhabditis elegans">Caenorhabditis elegans</a>For one example, </em>&nbsp;lacks cytosine methylation, produceswhile&nbsp;<a href="http://en.wikipedia.org/wiki/5-Methylcytosine" title="5-Methylcytosine" Vertebrate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Vertebrate">5-methylcytosinevertebrates</a>, which is important for&nbsp;<a href=have higher levels, with up to 1% of their DNA containing 5-methylcytosine.^{<a href="http://en.wikipedia.org/wiki/XDNA#cite_note-inactivation" title="X-inactivation69" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">X-chromosome inactivation[69]</a>.</sup id="cite_ref>&nbsp;Despite the importance of 5-68" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolatemethylcytosine, it can&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-68Deamination" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[68]title="Deamination">deaminate</a>}&nbsp;The average level of methylation varies between organisms&nbsp;&ndash; the worm&nbsp;<i>to leave a thymine base, so methylated cytosines are particularly prone to<a href="http://en.wikipedia.org/wiki/Caenorhabditis_elegans" title="Caenorhabditis elegansMutation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Mutation">Caenorhabditis elegansmutations</a>.</isup>&nbsp;lacks cytosine methylation, while&nbsp;<<a href="http://en.wikipedia.org/wiki/Vertebrate" title="VertebrateDNA#cite_note-70" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">vertebrates[70]</a></sup>&nbsp;have higher levelsOther base modifications include adenine methylation in bacteria, with up to 1% the presence of their DNA containing 5-methylcytosine.&nbsp;<sup id="cite_ref-69" a class="reference" style="linemw-height: 1em; unicode-bidi: -webkit-isolate;redirect"><a href="http://en.wikipedia.org/wiki/DNA#cite_note5-69hydroxymethylcytosine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white" title="5-space: nowrap;hydroxymethylcytosine">[69]5-hydroxymethylcytosine</a></sup>&nbsp;Despite in the importance of 5-methylcytosine, it can&nbsp;<a href="http://en.wikipedia.org/wiki/DeaminationBrain" titlestyle="Deamination" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Brain">deaminatebrain</a>&nbsp;to leave a thymine base, so methylated cytosines are particularly prone to^{<a href="http://en.wikipedia.org/wiki/Mutation" title="MutationDNA#cite_note-71" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">mutations[71]</a>.</sup id="cite_ref-70" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href>&nbsp;and the&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-70Glycosylation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Glycosylation">[70]glycosylation</a>}&nbsp;Other base modifications include adenine methylation in bacteria, of uracil to produce the presence of&quot;J-base&quot; in&nbsp;<a href="http://en.wikipedia.org/wiki/5-hydroxymethylcytosine" title="5-hydroxymethylcytosine" class="mw-redirectKinetoplastid" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">5-hydroxymethylcytosinetitle="Kinetoplastid">kinetoplastids</a>&nbsp;in the&nbsp;.^{<a href="http://en.wikipedia.org/wiki/Brain" title="BrainDNA#cite_note-72" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">brain[72]</a>,}<sup id><a href="cite_ref-71" class="reference" style="line-heighthttp: 1em; unicode-bidi: -webkit-isolate;"><a href="http:///en.wikipedia.org/wiki/DNA#cite_note-7173" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[7173]</a></sup>&nbsp;and the&nbsp;<a href/p> <h3>Damage</h3> <div class="http://en.wikipedia.org/wiki/Glycosylationrellink boilerplate further" titlestyle="Glycosylation" font-style="text: italic; padding-decorationleft: none1.6em; colormargin-bottom: rgb(11, 0, 128).5em; backgroundfont-imagefamily: sans-serif; font-size: 12.800000190734863px; line-height: none19.200000762939453px;">glycosylation</a>Further information:&nbsp;of uracil to produce the &quot;J-base&quot; in&nbsp;<a <a href="http://en.wikipedia.org/wiki/Kinetoplastid" title="KinetoplastidDNA_damage_(naturally_occurring)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">kinetoplastidstitle="DNA damage (naturally occurring)">DNA damage (naturally occurring)</a>.,&nbsp;<sup ida href="cite_ref-72" class="referencehttp://en.wikipedia.org/wiki/Mutation" style="linetext-heightdecoration: 1emnone; unicodecolor: rgb(11, 0, 128); background-bidiimage: -webkit-isolatenone;"><title="Mutation">Mutation</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-72DNA_damage_theory_of_aging" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[72]</a></sup><sup id="cite_ref-73" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-73" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[73]</a></sup></p><h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Damage">Damage</span></h3><div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_damage_(naturally_occurring)" title="DNA damage (naturally occurring)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA damage (naturally occurring)</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Mutation" title="Mutation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Mutation</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_damage_theory_of_aging" title="DNA title="DNA damage theory of aging" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA damage theory of aging</a></div> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:Benzopyrene_DNA_adduct_1JDG.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Benzopyrene_DNA_adduct_1JDG.png/220px-Benzopyrene_DNA_adduct_1JDG.png" widthstyle="220" height="305" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Benzopyrene_DNA_adduct_1JDG.png/330pxbackground-Benzopyrene_DNA_adduct_1JDG.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Benzopyrene_DNA_adduct_1JDG.png/440px-Benzopyrene_DNA_adduct_1JDG.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:305px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:Benzopyrene_DNA_adduct_1JDG.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>A&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Covalent" title="Covalent" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Covalent">covalent</a>&nbsp;<a href="http://en.wikipedia.org/wiki/Adduct" title="Adduct" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Adduct">adduct</a>&nbsp;between a<a href="http://en.wikipedia.org/wiki/Cytochrome_P450,_family_1,_member_A1" title="Cytochrome P450, family 1, member A1" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cytochrome P450, family 1, member A1">metabolically activated</a>&nbsp;form of<a href="http://en.wikipedia.org/wiki/Benzo(a)pyrene" title="Benzo(a)pyrene" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Benzo(a)pyrene">benzo[<iem>a</iem>]pyrene</a>, the major&nbsp;<a href="http://en.wikipedia.org/wiki/Mutagen" title="Mutagen" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Mutagen">mutagen</a>&nbsp;in<a href="http://en.wikipedia.org/wiki/Tobacco_smoking" title="Tobacco smoking" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Tobacco smoking">tobacco smoke</a>, and DNA<sup id="cite_ref-74" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-74" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[74]</a></sup></div>

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:T7_RNA_polymerase.jpg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/T7_RNA_polymerase.jpg/220px-T7_RNA_polymerase.jpg" widthstyle="220" height="170" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e3/T7_RNA_polymerase.jpg/330pxbackground-T7_RNA_polymerase.jpg 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/e/e3/T7_RNA_polymerase.jpg/440px-T7_RNA_polymerase.jpg 2x" style="255); border: 1px solid rgb(204, 204, 204); height:170px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:T7_RNA_polymerase.jpg" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div><a href="http://en.wikipedia.org/wiki/T7_RNA_polymerase" title="T7 RNA polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="T7 RNA polymerase">T7 RNA polymerase</a>&nbsp;(blue) producing a mRNA (green) from a DNA template (orange).<sup id="cite_ref-93" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-93" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[93]</a></sup></div>

 <p style>Some noncoding DNA sequences play structural roles in chromosomes.&nbsp;<a href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Telomere" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serif; fontrgb(11, 0, 128); background-sizeimage: 12.800000190734863pxnone;">Some noncoding DNA sequences play structural roles in chromosomes.&nbsp;<a hreftitle="Telomere">Telomeres</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Telomere" title="TelomereCentromere" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Telomerestitle="Centromere">centromeres</a>&nbsp;typically contain few genes, but are important for the function and&nbsp;stability of chromosomes.^{<a href="http://en.wikipedia.org/wiki/Centromere" title="CentromereDNA#cite_note-Nugent-56" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">centromeres[56]</a>&nbsp;typically contain few genes, but are important for the function and stability of chromosomes.<sup id/sup>^{<a href="cite_ref-Nugent_56-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-Nugent-5694" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5694]</a>}&nbsp;An abundant form of noncoding DNA in humans are&nbsp;<sup ida href="cite_ref-94" class="referencehttp://en.wikipedia.org/wiki/Pseudogene" style="linetext-heightdecoration: 1emnone; unicode-bidicolor: rgb(11, 0, 128); background-webkit-isolateimage: none;"title="Pseudogene">pseudogenes</a>, which are copies of genes that have been disabled by mutation.^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-9495" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[9495]</a>}&nbsp;An abundant form of noncoding DNA in humans These sequences areusually just molecular&nbsp;<a href="http://en.wikipedia.org/wiki/Pseudogene" title="PseudogeneFossil" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Fossil">pseudogenesfossils</a>, which are copies although they can occasionally serve as raw genetic material for the creation of new genes that have been disabled by mutation.<sup id="cite_ref-95" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">through the process of&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-95" Gene_duplication" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Gene duplication">[95]gene duplication</a>}&nbsp;These sequences are usually just molecular&nbspand&nbsp;<a href="http://en.wikipedia.org/wiki/Fossil" title="FossilDivergent_evolution" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Divergent evolution">fossilsdivergence</a>, although they can occasionally serve as raw genetic material for the creation of new genes through the process of&nbsp;<.<sup><a href="http://en.wikipedia.org/wiki/Gene_duplicationDNA#cite_note-96" titlestyle="Gene duplication" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">gene duplication[96]</a>&nbsp;and&nbsp;<a href="http:/sup></en.wikipedia.orgp> <h3>Transcription and translation</wiki/Divergent_evolutionh3> <div class=" title="Divergent evolutionrellink boilerplate further" style="textfont-decorationstyle: noneitalic; colorpadding-left: rgb(11, 0, 128)1.6em; backgroundmargin-imagebottom: none0.5em;">divergence</a>.<sup id="cite_reffont-family: sans-96" class="reference" style="lineserif; font-heightsize: 1em12.800000190734863px; unicodeline-bidiheight: -webkit-isolate19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-96" styleGenetic_code" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Genetic code">[96]Genetic code</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/sup></p><h3 Transcription_(genetics)" style="backgroundtext-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflow: hidden; paddingbackground-topimage: 0.5emnone; padding-bottom: 0.17em" title="Transcription (genetics)">Transcription (genetics)</a>,&nbsp; border-bottom-style<a href="http: none; font//en.wikipedia.org/wiki/Protein_biosynthesis" style="text-sizedecoration: 16.799999237060547pxnone; font-familycolor: sans-serifrgb(11, 0, 128); linebackground-heightimage: 19.200000762939453pxnone;"><span classtitle="mw-headline" id="Transcription_and_translationProtein biosynthesis">Transcription and translationProtein biosynthesis</spana></h3div> <p>A gene is a sequence of DNA that contains genetic information and can influence the&nbsp;<div classa href="rellink boilerplate furtherhttp://en.wikipedia.org/wiki/Phenotype" style="fonttext-styledecoration: italicnone; padding-left: 1.6em; margin-bottomcolor: rgb(11, 0.5em, 128); fontbackground-familyimage: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453pxnone;"title="Phenotype">phenotype</a>Further information:&nbsp;<of an organism. Within a href=gene, the sequence of bases along a DNA strand defines a&nbsp;<a href="http://en.wikipedia.org/wiki/Genetic_code" title="Genetic codeMessenger_RNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Messenger RNA">Genetic codemessenger RNA</a>&nbsp;sequence,which then defines one or more protein sequences. The relationship between the nucleotide sequences of genes and the&nbsp;<a href="http://en.wikipedia.org/wiki/Transcription_(genetics)" title="Transcription (genetics)" Amino_acid" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Amino acid">Transcription (genetics)amino-acid</a>,&nbsp;<a sequences of proteins is determined by the rules of&nbsp;<a href="http://en.wikipedia.org/wiki/Protein_biosynthesis" title="Protein biosynthesisTranslation_(biology)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Protein biosynthesistitle="Translation (biology)">translation</a>, known collectively as the&nbsp;</div><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Genetic_code" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="Genetic code">A gene is genetic code</a sequence of DNA that contains >. The genetic information and can influence thecode consists of three-letter &#39;words&#39; called&nbsp;<a href="http:em>codons<//enem>&nbsp;formed from a sequence of three nucleotides (e.g.wikipediaACT, CAG, TTT).org</wiki/Phenotypep> <p>In transcription, the codons of a gene are copied into messenger RNA by&nbsp;<a href=" title="Phenotypehttp://en.wikipedia.org/wiki/RNA_polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="RNA polymerase">phenotypeRNA polymerase</a>&nbsp;of an organism. Within a gene, the sequence of bases along a DNA strand defines . This RNA copy is then decoded by a&nbsp;<a href="http://en.wikipedia.org/wiki/Messenger_RNARibosome" titlestyle="Messenger RNA" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ribosome">messenger RNAribosome</a>that reads the RNA sequence by base-pairing the messenger RNA to&nbsp;sequence, which then defines one or more protein sequences. The relationship between the nucleotide sequences of genes and the&nbsp;<a <a href="http://en.wikipedia.org/wiki/Amino_acidTransfer_RNA" titlestyle="Amino acid" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Transfer RNA">amino-acidtransfer RNA</a>&nbsp;sequences of proteins is determined by the rules of&nbsp;, which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (<a hrefimg alt="4^3" class="tex" src="http://enupload.wikipediawikimedia.org/wikimath/2/9/b/Translation_(biology)" title="Translation (biology)29b8a6aa9d0f15d19fae3aa4c6d6c883.png" style="text-decorationborder: none; colormargin: rgb(11, 0, 128)0px; backgroundvertical-imagealign: none;middle">translation</a>, known collectively as &nbsp;combinations). These encode thetwenty&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Genetic_codeList_of_standard_amino_acids" titlestyle="Genetic code" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="List of standard amino acids">genetic codestandard amino acids</a>. The genetic code consists of , giving most amino acids more than one possible codon. There are also three-letter 'words' called&nbsp#39;<i>codons</i>stop&nbsp#39;formed from a sequence or &#39;nonsense&#39; codons signifying the end of three nucleotides (e.g. ACTthe coding region; these are the TAA, CAG, TTT).</p><p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In transcription, the codons of a gene are copied into messenger RNA by&nbsp;<a href="http://en.wikipedia.org/wiki/RNA_polymerase" title="RNA polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">RNA polymerase</a>. This RNA copy is then decoded by a&nbsp;<a href="http://en.wikipedia.org/wiki/Ribosome" title="Ribosome" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ribosome</a>that reads the RNA sequence by base-pairing the messenger RNA to&nbsp;<a href="http://en.wikipedia.org/wiki/Transfer_RNA" title="Transfer RNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">transfer RNA</a>, which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (<img class="tex" alt="4^3" src="http://upload.wikimedia.org/math/2/9/b/29b8a6aa9d0f15d19fae3aa4c6d6c883.png" style="border: none; vertical-align: middle; margin: 0px;" />&nbsp;combinations). These encode the twenty&nbsp;<a href="http://en.wikipedia.org/wiki/List_of_standard_amino_acids" title="List of standard amino acids" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">standard amino acids</a>, giving most amino acids more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region; these are the TAA, TGA and TGA and TAG codons.</p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 452px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:DNA_replication_en.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/DNA_replication_en.svg/450px-DNA_replication_en.svg.png" widthstyle="450" height="219" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8f/DNA_replication_en.svg/675pxbackground-DNA_replication_en.svg.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/8/8f/DNA_replication_en.svg/900px-DNA_replication_en.svg.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:219px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);450px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:DNA_replication_en.svg" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>DNA replication. The double helix is unwound by a&nbsp;<a href="http://en.wikipedia.org/wiki/Helicase" title="Helicase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Helicase">helicase</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Topoisomerase" title="Topoisomerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Topoisomerase">topoisomerase</a>. Next, one&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_polymerase" title="DNA polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA polymerase">DNA polymerase</a>&nbsp;produces the&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Replication_fork" title="Replication fork" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Replication fork">leading strand</a>&nbsp;copy. Another DNA polymerase binds to the&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Replication_fork" title="Replication fork" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Replication fork">lagging strand</a>. This enzyme makes discontinuous segments (called&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Okazaki_fragment" title="Okazaki fragment" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Okazaki fragment">Okazaki fragments</a>) before&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_ligase" title="DNA ligase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA ligase">DNA ligase</a>&nbsp;joins them together.</div>

 <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Replication">Replication</span></h3> <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_replication" title="DNA replication" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA replication">DNA replication</a></div> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;"><a href="http://en.wikipedia.org/wiki/Cell_division" title="Cell division" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cell division">Cell division</a>&nbsp;is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. The double-stranded structure of DNA provides a simple mechanism for&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_replication" title="DNA replication" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA replication">DNA replication</a>. Here, the two strands are separated and then each strand'&#39;s&nbsp;<a href="http://en.wikipedia.org/wiki/Complementary_DNA" title="Complementary DNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Complementary DNA">complementary DNA</a>&nbsp;sequence is recreated by an<a href="http://en.wikipedia.org/wiki/Enzyme" title="Enzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Enzyme">enzyme</a>&nbsp;called&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_polymerase" title="DNA polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA polymerase">DNA polymerase</a>. This enzyme makes the complementary strand by finding the correct base through complementary base pairing, and bonding it onto the original strand. As DNA polymerases can only extend a DNA strand in a 5&prime; to 3&prime; direction, different mechanisms are used to copy the antiparallel strands of the double helix.<sup id="cite_ref-97" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-97" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[97]</a></sup>&nbsp;In this way, the base on the old strand dictates which base appears on the new strand, and the cell ends up with a perfect copy of its DNA.</p> <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Interactions_with_proteins">Interactions with proteins</span></h2> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">All the functions of DNA depend on interactions with proteins. These&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Protein_interactions" title="Protein interactions" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Protein interactions">protein interactions</a>&nbsp;can be non-specific, or the protein can bind specifically to a single DNA sequence. Enzymes can also bind to DNA and of these, the polymerases that copy the DNA base sequence in transcription and DNA replication are particularly important.</p> <h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="DNA-binding_proteins">DNA-binding proteins</span></h3> <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA-binding_protein" title="DNA-binding protein" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA-binding protein">DNA-binding protein</a></div> 

<table border="0" cellpadding="0" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 260px; margin: 0.3em;width:260px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Nucleosome1.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Nucleosome1.png" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Nucleosome1.png/260px-Nucleosome1.png" width="260" height="171" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/Nucleosome1.png/390px-Nucleosome1.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/be/Nucleosome1.png/520px-Nucleosome1.png 2x" style="border: none; height:171px; vertical-align: middle;width:260px" /></a></td> </tr> <tr> <td>&nbsp;</td> </tr> </tbody>

<div class="thumbcaption" style="border: none; line-height: 1.4em; font-size: 12px; padding: 3px !important;">Interaction of DNA (shown in orange) with<a href="http://en.wikipedia.org/wiki/Histone" title="Histone" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Histone">histones</a>&nbsp;(shown in blue). These proteins' &#39; basic amino acids bind to the acidic phosphate groups on DNA.</div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called&nbsp;<a href="http://en.wikipedia.org/wiki/Chromatin" titlestyle="Chromatin" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Chromatin">chromatin</a>. In eukaryotes this structure involves DNA binding to a complex of small basic proteins called&nbsp;<a href="http://en.wikipedia.org/wiki/Histone" title="Histone" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Histone">histones</a>, while in prokaryotes multiple types of proteins are involved.<sup id><a href="cite_ref-98" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:http://en.wikipedia.org/wiki/DNA#cite_note-98" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[98]</a></sup><sup id="cite_ref-99" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href><a href="http://en.wikipedia.org/wiki/DNA#cite_note-99" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[99]</a></sup>&nbsp;The histones form a disk-shaped complex called a&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleosome" titlestyle="Nucleosome" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleosome">nucleosome</a>, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones making<a href="http://en.wikipedia.org/wiki/Ionic_bond" title="Ionic bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ionic bond">ionic bonds</a>&nbsp;to the acidic sugar-phosphate backbone of the DNA, and are therefore largely independent of the base sequence.<sup id><a href="cite_ref-100" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-100" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[100]</a></sup>Chemical modifications of these basic amino acid residues include&nbsp;<a href="http://en.wikipedia.org/wiki/Methylation" titlestyle="Methylation" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Methylation">methylation</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Phosphorylation" title="Phosphorylation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Phosphorylation">phosphorylation</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Acetylation" title="Acetylation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Acetylation">acetylation</a>.<sup id="cite_ref-101" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-101" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[101]</a></sup>&nbsp;These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to<a href="http://en.wikipedia.org/wiki/Transcription_factor" titlestyle="Transcription factor" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Transcription factor">transcription factors</a>&nbsp;and changing the rate of transcription.<sup id><a href="cite_ref-102" class="reference" style="line-heighthttp: 1em; unicode-bidi: -webkit-isolate;"><a href="http:///en.wikipedia.org/wiki/DNA#cite_note-102" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[102]</a></sup>&nbsp;Other non-specific DNA-binding proteins in chromatin include the high-mobility group proteins, which bind to bent or distorted DNA.<sup id><a href="cite_ref-103" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://http://en.wikipedia.org/wiki/DNA#cite_note-103" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[103]</a></sup>&nbsp;These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up chromosomes.<sup id="cite_ref-104" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href><a href="http://en.wikipedia.org/wiki/DNA#cite_note-104" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[104]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">A >A distinct group of DNA-binding proteins are the DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication<a href="http://en.wikipedia.org/wiki/Protein_A" titlestyle="Protein A" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Protein A">protein A</a>&nbsp;is the best-understood member of this family and is used in processes where the double helix is separated, including DNA replication, recombination and DNA repair.<sup id><a href="cite_ref-105" class="reference" style="line-heighthttp: 1em; unicode-bidi: -webkit-isolate;"><a href="http:///en.wikipedia.org/wiki/DNA#cite_note-105" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[105]</a></sup>&nbsp;These binding proteins seem to stabilize single-stranded DNA and protect it from forming&nbsp;<a href="http://en.wikipedia.org/wiki/Stem-loop" title="Stem-loop" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Stem-loop">stem-loops</a>&nbsp;or being degraded by&nbsp;<a href="http://en.wikipedia.org/wiki/Nuclease" title="Nuclease" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nuclease">nucleases</a>.</p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 172px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:Lambda_repressor_1LMB.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Lambda_repressor_1LMB.png/170px-Lambda_repressor_1LMB.png" widthstyle="170" height="250" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Lambda_repressor_1LMB.png/255pxbackground-Lambda_repressor_1LMB.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Lambda_repressor_1LMB.png/340px-Lambda_repressor_1LMB.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:250px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);170px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:Lambda_repressor_1LMB.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>The lambda repressor&nbsp;<a href="http://en.wikipedia.org/wiki/Helix-turn-helix" title="Helix-turn-helix" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Helix-turn-helix">helix-turn-helix</a>&nbsp;transcription factor bound to its DNA target<sup id="cite_ref-106" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-106" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[106]</a></sup></div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In contrast, other proteins have evolved to bind to particular DNA sequences. The most intensively studied of these are the various&nbsp;<a href="http://en.wikipedia.org/wiki/Transcription_factor" title="Transcription factor" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Transcription factor">transcription factors</a>, which are proteins that regulate transcription. Each transcription factor binds to one particular set of DNA sequences and activates or inhibits the transcription of genes that have these sequences close to their promoters. The transcription factors do this in two ways. Firstly, they can bind the RNA polymerase responsible for transcription, either directly or through other mediator proteins; this locates the polymerase at the promoter and allows it to begin transcription.<sup id="cite_ref-107" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-107" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[107]</a></sup>&nbsp;Alternatively, transcription factors can bind&nbsp;<a href="http://en.wikipedia.org/wiki/Enzyme" title="Enzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Enzyme">enzymes</a>&nbsp;that modify the histones at the promoter. This changes the accessibility of the DNA template to the polymerase.<sup id="cite_ref-108" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-108" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[108]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">As these DNA targets can occur throughout an organism'&#39;s genome, changes in the activity of one type of transcription factor can affect thousands of genes.<sup id="cite_ref-109" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-109" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[109]</a></sup>&nbsp;Consequently, these proteins are often the targets of the&nbsp;<a href="http://en.wikipedia.org/wiki/Signal_transduction" title="Signal transduction" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Signal transduction">signal transduction</a>&nbsp;processes that control responses to environmental changes or&nbsp;<a href="http://en.wikipedia.org/wiki/Cellular_differentiation" title="Cellular differentiation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Cellular differentiation">cellular differentiation</a>&nbsp;and development. The specificity of these transcription factors' &#39; interactions with DNA come from the proteins making multiple contacts to the edges of the DNA bases, allowing them to &quot;read&quot; the DNA sequence. Most of these base-interactions are made in the major groove, where the bases are most accessible.<sup id="cite_ref-Pabo1984_25-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Pabo1984-25" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[25]</a></sup></p> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:EcoRV_1RVA.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/EcoRV_1RVA.png/220px-EcoRV_1RVA.png" widthstyle="220" height="154" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/EcoRV_1RVA.png/330pxbackground-EcoRV_1RVA.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/d/dc/EcoRV_1RVA.png/440px-EcoRV_1RVA.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:154px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:EcoRV_1RVA.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>The&nbsp;<a href="http://en.wikipedia.org/wiki/Restriction_enzyme" title="Restriction enzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Restriction enzyme">restriction enzyme</a>&nbsp;<a href="http://en.wikipedia.org/wiki/EcoRV" title="EcoRV" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="EcoRV">EcoRV</a>(green) in a complex with its substrate DNA<sup id="cite_ref-110" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-110" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[110]</a></sup></div>

 <h3>DNA-modifying enzymes</h3 style> <h4>Nucleases and ligases</h4> <p><a href="background-imagehttp: none; margin: 0px 0px 0//en.wikipedia.3em; overflow: hidden; paddingorg/wiki/Nuclease" style="text-topdecoration: 0.5emnone; padding-bottomcolor: rgb(11, 0.17em, 128); borderbackground-bottom-styleimage: none; font-size: 16.799999237060547px; font-family: sans-serif; line-height: 19.200000762939453px;"><span classtitle="mw-headline" id="DNA-modifying_enzymesNuclease">DNA-modifying enzymesNucleases</spana>&nbsp;are&nbsp;<a href="http://en.wikipedia.org/h3><h4 wiki/Enzyme" style="backgroundtext-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflow: hidden; paddingbackground-top: 0.5em; padding-bottom: 0.17em; border-bottom-styleimage: none; font-size: 15.199999809265137px; font-family: sans-serif; line-height: 19.200000762939453px;"><span classtitle="mw-headline" id="Nucleases_and_ligasesEnzyme">Nucleases and ligasesenzymes</spana>&nbsp;that cut DNA strands by catalyzing the&nbsp;</h4><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;"><a href="http://en.wikipedia.org/wiki/Nuclease" title="Nucleaseorg/wiki/Hydrolysis" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydrolysis">Nucleaseshydrolysis</a>&nbsp;areof the&nbsp;<a href="http://en.wikipedia.org/wiki/Enzyme" title="EnzymePhosphodiester_bond" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Phosphodiester bond">enzymesphosphodiester bonds</a>&nbsp;. Nucleases that cut hydrolyse nucleotides from the ends of DNA strands by catalyzing theare called&nbsp;<a href="http://en.wikipedia.org/wiki/Hydrolysis" title="HydrolysisExonuclease" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Exonuclease">hydrolysisexonucleases</a>&nbsp;of the&nbsp;, while<a href="http://en.wikipedia.org/wiki/Phosphodiester_bond" title="Phosphodiester bondEndonuclease" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Endonuclease">phosphodiester bondsendonucleases</a>. Nucleases that hydrolyse nucleotides from the ends of DNA strands are called&nbsp;<a hrefcut within strands. The most frequently used nucleases in&nbsp;<a href="http://en.wikipedia.org/wiki/Exonuclease" title="ExonucleaseMolecular_biology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Molecular biology">exonucleasesmolecular biology</a>, while&nbsp;are the<a href="http://en.wikipedia.org/wiki/Endonuclease" title="EndonucleaseRestriction_enzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">endonucleasestitle="Restriction enzyme">restriction endonucleases</a>&nbsp;, which cut within strandsDNA at specific sequences. The most frequently used nucleases inFor instance, the EcoRV enzyme shown to the left recognizes the 6-base sequence 5&nbspprime;<-GATATC-3&prime; and makes a cut at the vertical line. In nature, these enzymes protect&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_biology" title="Molecular biologyBacteria" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bacteria">molecular biologybacteria</a>&nbsp;are theagainst&nbsp;<a href="http://en.wikipedia.org/wiki/Restriction_enzyme" title="Restriction enzymeBacteriophage" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Bacteriophage">restriction endonucleasesphage</a>, which cut &nbsp;infection by digesting the phage DNA at specific sequences. For instancewhen it enters the bacterial cell, acting as part of the EcoRV enzyme shown to the left recognizes the 6-base sequence 5&prime;-GATATC-3&prime; and makes a cut at the vertical line. In nature, these enzymes protect&nbsp&nbsp;<a href="http://en.wikipedia.org/wiki/Bacteria" title="BacteriaRestriction_modification_system" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Restriction modification system">bacteriarestriction modification system</a>&nbsp;against&nbsp;.^{<a href="http://en.wikipedia.org/wiki/Bacteriophage" title="BacteriophageDNA#cite_note-111" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">phage[111]</a>&}&nbsp;infection by digesting the phage DNA when it enters the bacterial cellIn technology, acting as part of thethese sequence-specific nucleases are used in&nbsp;<a href="http://en.wikipedia.org/wiki/Restriction_modification_system" title="Restriction modification systemMolecular_cloning" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Molecular cloning">restriction modification systemmolecular cloning</a>.&nbsp;and&nbsp;<sup id="cite_ref-111" a class="reference" style="linemw-height: 1em; unicode-bidi: -webkit-isolate;redirect"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-111Genetic_fingerprinting" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Genetic fingerprinting">[111]DNA fingerprinting</a>.</supp> <p>&nbsp;In technology, these sequence-specific nucleases are used inEnzymes called&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_cloning" title="Molecular cloningDNA_ligase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA ligase">molecular cloningDNA ligases</a>&nbsp;and&nbsp;can rejoin cut or broken DNA strands.^{<a href="http://en.wikipedia.org/wiki/Genetic_fingerprinting" title="Genetic fingerprinting" class="mwDNA#cite_note-Doherty-redirect112" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">DNA fingerprinting[112]</a>.</psup>&nbsp;Ligases are particularly important in&nbsp;<p stylea class="mw-redirect" href="marginhttp: 0//en.4em 0px 0wikipedia.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">Enzymes called&nbsp;<a href="http://en.wikipedia.orgorg/wiki/DNA_ligase" title="DNA ligaseReplication_fork" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA ligasestitle="Replication fork">lagging strand</a>&nbsp;can rejoin cut or broken DNA strands.replication, as they join together the short segments of DNA produced at the&nbsp;<sup ida class="cite_refmw-Doherty_112-0redirect" classhref="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-Doherty-112Replication_fork" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Replication fork">[112]replication fork</a>}&&nbsp;Ligases into a complete copy of the DNA template. They are particularly important also used in&nbsp;<a href="http://en.wikipedia.org/wiki/Replication_fork" title="Replication fork" class="mw-redirectDNA_repair" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA repair">lagging strandDNA repair</a>&nbsp;DNA replication, as they join together the short segments of DNA produced at theand&nbsp;<a href="http://en.wikipedia.org/wiki/Replication_fork" title="Replication fork" class="mw-redirectGenetic_recombination" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic recombination">replication forkgenetic recombination</a>&nbsp;into a complete copy of the DNA template. They are also used in&nbsp;.^{<a href="http://en.wikipedia.org/wiki/DNA_repair" title="DNA repair#cite_note-Doherty-112" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">DNA repair[112]</a>&nbsp;}</p> <h4>Topoisomerases and&nbsp;helicases</h4> <p><a href="http://en.wikipedia.org/wiki/Genetic_recombination" title="Genetic recombinationTopoisomerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Topoisomerase">genetic recombinationTopoisomerases</a>.<sup id="cite_ref-Doherty_112-1" class="reference" style="line-height: 1em&nbsp;are enzymes with both nuclease and ligase activity. These proteins change the amount of&nbsp; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Doherty-112" styleDNA_supercoil" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="DNA supercoil">[112]supercoiling</a></sup></p><h4 style="background-image: none&nbsp; margin: 0px 0px 0in DNA.3emSome of these enzymes work by cutting the DNA helix and allowing one section to rotate, thereby reducing its level of supercoiling; overflow: hidden; padding-top: 0the enzyme then seals the DNA break.5em; padding-bottom^{<a href="http: 0//en.wikipedia.17em; borderorg/wiki/DNA#cite_note-bottomChampoux-37" style="text-decoration: none; font-sizecolor: 15.199999809265137pxrgb(11, 0, 128); fontbackground-familyimage: sans-serifnone; linewhite-heightspace: 19.200000762939453pxnowrap;"><span class="mw-headline" id="Topoisomerases_and_helicases">Topoisomerases and helicases[37]</spana></h4sup><p style="margin: 0.4em 0px 0.5em&nbsp; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12Other types of these enzymes are capable of cutting one DNA helix and then passing a second strand of DNA through this break, before rejoining the helix.800000190734863px;"^{<a href="http://en.wikipedia.org/wiki/Topoisomerase" title="TopoisomeraseDNA#cite_note-113" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">Topoisomerases[113]</a>}&nbsp;Topoisomerases are enzymes with both nuclease required for many processes involving DNA, such as DNA replication and ligase activitytranscription. These proteins change the amount of&nbsp;^{<a href="http://en.wikipedia.org/wiki/DNA_supercoil" title="DNA supercoil#cite_note-Wang-38" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">supercoiling[38]</a>&nbsp;in DNA}</p> <p><a href="http://en.wikipedia. Some of these enzymes work by cutting the DNA helix and allowing one section to rotate, thereby reducing its level of supercoiling; the enzyme then seals the DNA break.<sup id="cite_ref-Champoux_37-1" class="referenceorg/wiki/Helicase" style="linetext-heightdecoration: 1emnone; unicodecolor: rgb(11, 0, 128); background-bidiimage: -webkit-isolatenone;" title="Helicase">Helicases</a>&nbsp;are proteins that are a type of&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-Champoux-37" styleMolecular_motor" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Molecular motor">[37]molecular motor</a>}. They use the chemical energy in&nbsp;Other types of these enzymes are capable of cutting one DNA helix and then passing a second strand of DNA through this break, before rejoining the helix<a href="http://en.wikipedia.<sup id="cite_ref-113" class="referenceorg/wiki/Nucleoside_triphosphate" style="linetext-heightdecoration: 1emnone; unicodecolor: rgb(11, 0, 128); background-bidiimage: -webkit-isolatenone;"title="Nucleoside triphosphate">nucleoside triphosphates</a>, predominantly&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-113Adenosine_triphosphate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Adenosine triphosphate">[113]ATP</a></sup>&nbsp;Topoisomerases are required for many processes involving DNA, such as to break hydrogen bonds between bases and unwind the DNA replication and transcriptiondouble helix into single strands.<sup id="cite_ref-Wang_38-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Wang-38114" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[38114]</a></sup></p><p style="margin: 0.4em 0px 0.5em&nbsp; line-height: 19These enzymes are essential for most processes where enzymes need to access the DNA bases.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;"</p> <h4>Polymerases</h4> <p><a href="http://en.wikipedia.org/wiki/Helicase" title="HelicasePolymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Polymerase">HelicasesPolymerases</a>&nbsp;are proteins that are a type of&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_motor" title="Molecular motorEnzyme" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Enzyme">molecular motorenzymes</a>. They use the chemical energy in&nbsp;<that synthesize polynucleotide chains from&nbsp;<a href="http://en.wikipedia.org/wiki/Nucleoside_triphosphate" title="Nucleoside triphosphate" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleoside triphosphate">nucleoside triphosphates</a>, predominantly. The sequence of their products are copies of existing polynucleotide chains&mdash;which are called&nbsp;<a href=em>templates</em>. These enzymes function by adding nucleotides onto the 3&prime;&nbsp;<a href="http://en.wikipedia.org/wiki/Adenosine_triphosphate" title="Adenosine triphosphateHydroxyl" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hydroxyl">ATPhydroxyl group</a>, to break hydrogen bonds between bases and unwind the &nbsp;of the previous nucleotide in a DNA double helix into single strandsstrand. As a consequence, all polymerases work in a 5&prime; to 3&prime; direction.<sup id><a href="cite_ref-114" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-114Joyce-115" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[114115]</a></sup>&nbsp;These enzymes are essential for most processes where enzymes need to access In the DNA bases&nbsp;<a href="http://en.wikipedia.<org/wiki/p><h4 Active_site" style="backgroundtext-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflowbackground-image: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none; font-size: 15.199999809265137px; font-family: sans-serif; line-height: 19.200000762939453pxnone;"><span classtitle="mw-headline" id="PolymerasesActive site">Polymerasesactive site</spana><&nbsp;of these enzymes, the incoming nucleoside triphosphate base-pairs to the template: this allows polymerases to accurately synthesize the complementary strand of their template. Polymerases are classified according to the type of template that they use.</h4p> <p style="margin: 0.4em 0px 0.5em; line>In DNA replication, a DNA-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863pxdependent&nbsp;"><a href="http://en.wikipedia.org/wiki/Polymerase" title="PolymeraseDNA_polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA polymerase">PolymerasesDNA polymerase</a>&nbsp;aremakes a copy of a DNA sequence. Accuracy is vital in this process, so many of these polymerases have a&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Enzyme" title="EnzymeProofreading_(Biology)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">enzymestitle="Proofreading (Biology)">proofreading</a>&nbsp;that synthesize polynucleotide chains from&nbsp;<a href="http://enactivity.wikipedia.org/wiki/Nucleoside_triphosphate" titleHere, the polymerase recognizes the occasional mistakes in the synthesis reaction by the lack of base pairing between the mismatched nucleotides. If a mismatch is detected, a 3&prime; to 5&prime;&nbsp;<a href="Nucleoside triphosphate" style="text-decorationhttp://en.wikipedia.org/wiki/Exonuclease" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Exonuclease">nucleoside triphosphatesexonuclease</a>. The sequence of their products are copies of existing polynucleotide chains&mdash;which are called&nbsp;activity is activated and the incorrect base removed.<i>templates</isup>. These enzymes function by adding nucleotides onto the 3&prime;&nbsp;<a href="http://en.wikipedia.org/wiki/Hydroxyl" title="HydroxylDNA#cite_note-116" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">hydroxyl group[116]</a></sup>&nbsp;of the previous nucleotide in a In most organisms, DNA strand. As a consequence, all polymerases work function in a 5large complex called the&primenbsp; to 3&prime; direction.<sup ida href="cite_ref-Joyce_115-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-Joyce-115Replisome" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Replisome">[115]replisome</a></sup>&nbsp;In that contains multiple accessory subunits, such as the&nbsp;<a href="http://en.wikipedia.org/wiki/Active_site" title="Active siteDNA_clamp" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA clamp">active siteDNA clamp</a>&nbsp;of these enzymes, the incoming nucleoside triphosphate base-pairs to the templateor&nbsp;<a href="http: this allows polymerases to accurately synthesize the complementary strand of their template//en. Polymerases are classified according to the type of template that they usewikipedia.<org/wiki/p><p Helicase" style="margin: 0.4em 0px 0.5em; linetext-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="Helicase">In DNA replication, helicases</a DNA-dependent&nbsp;>.^{<a href="http://en.wikipedia.org/wiki/DNA_polymerase" title="DNA polymerase#cite_note-117" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">DNA polymerase[117]</a>&nbsp;makes a copy of a}</p> <p>RNA-dependent DNA polymerases are a specialized class of polymerases that copy the sequenceof an RNA strand into DNA. Accuracy is vital in this process, so many of these polymerases have aThey include&nbsp;<a href="http://en.wikipedia.org/wiki/Proofreading_(Biology)Reverse_transcriptase" title="Proofreading (Biology)" class="mw-redirect" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Reverse transcriptase">proofreadingreverse transcriptase</a>, which is a&nbsp;activity<a href="http://en.wikipedia. Here, the polymerase recognizes the occasional mistakes in the synthesis reaction by the lack of base pairing between the mismatched nucleotides. If a mismatch is detected, a 3&primeorg/wiki/Virus" style="text-decoration: none; to 5&primecolor: rgb(11, 0, 128); background-image: none;" title="Virus">viral</a>enzyme involved in the infection of cells by&nbsp;<a href="http://en.wikipedia.org/wiki/Exonuclease" title="ExonucleaseRetrovirus" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">exonucleasetitle="Retrovirus">retroviruses</a>, and&nbsp;activity is activated and the incorrect base removed.<sup id="cite_ref-116" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-116" Telomerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Telomerase">[116]telomerase</a>, which is required for the replication of telomeres.</sup>&nbsp;In most organisms, DNA polymerases function in <a large complex called the&nbsp;<a href=href="http://en.wikipedia.org/wiki/Replisome" title="ReplisomeDNA#cite_note-Greider-55" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">replisome[55]</a>&nbsp;that contains multiple accessory subunits, such as the&nbsp;</sup>^{<a href="http://en.wikipedia.org/wiki/DNA_clamp" title="DNA clamp#cite_note-118" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">DNA clamp[118]</a>}&nbsp;or&nbsp;<a Telomerase is an unusual polymerase because it contains its own RNA template as part of its structure.^{<a href="http://en.wikipedia.org/wiki/Helicase" title="HelicaseDNA#cite_note-Nugent-56" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">helicases[56]</a>.</sup id="cite_ref></p> <p>Transcription is carried out by a DNA-117" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolatedependent&nbsp;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-117RNA_polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="RNA polymerase">[117]RNA polymerase</a>}</p><p style="margin: 0.4em 0px 0.5em&nbsp; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12that copies the sequence of a DNA strand into RNA.800000190734863px;">To begin transcribing a gene, the RNA-dependent DNA polymerases are polymerase binds to a specialized class of polymerases that copy the sequence of an RNA strand into DNA. They includecalled a promoter and separates the DNA strands. It then copies the gene sequence into a&nbsp;<a href="http://en.wikipedia.org/wiki/Reverse_transcriptase" title="Reverse transcriptaseMessenger_RNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Messenger RNA">reverse transcriptasemessenger RNA</a>, which is a&nbsp;transcript until it reaches a region of DNA called the<a href="http://en.wikipedia.org/wiki/Virus" title="VirusTerminator_(genetics)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Terminator (genetics)">viralterminator</a>enzyme involved in , where it halts and detaches from the infection of cells byDNA. As with human DNA-dependent DNA polymerases,&nbsp;<a href="http://en.wikipedia.org/wiki/Retrovirus" title="RetrovirusRNA_polymerase_II" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="RNA polymerase II">retrovirusesRNA polymerase II</a>, andthe enzyme that transcribes most of the genes in the human genome, operates as part of a large&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/TelomeraseProtein_complex" title="Telomerase" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Protein complex">telomeraseprotein complex</a>, which is required for the replication of telomeres&nbsp;with multiple regulatory and accessory subunits.<sup id><a href="cite_ref-Greider_55-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://enhttp://en.wikipedia.org/wiki/DNA#cite_note-Greider-55119" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[55119]</a></sup><sup id="cite_ref-118" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-118" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[118]</a></sup>&nbsp;Telomerase is an unusual polymerase because it contains its own RNA template as part of its structure.<sup id="cite_ref-Nugent_56-2" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Nugent-56" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[56]</a></sup></p><p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">Transcription is carried out by a DNA-dependent&nbsp;<a href="http://en.wikipedia.org/wiki/RNA_polymerase" title="RNA polymerase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">RNA polymerase</a>&nbsp;that copies the sequence of a DNA strand into RNA. To begin transcribing a gene, the RNA polymerase binds to a sequence of DNA called a promoter and separates the DNA strands. It then copies the gene sequence into a&nbsp;<a href="http://en.wikipedia.org/wiki/Messenger_RNA" title="Messenger RNA" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">messenger RNA</a>&nbsp;transcript until it reaches a region of DNA called the<a href="http://en.wikipedia.org/wiki/Terminator_(genetics)" title="Terminator (genetics)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">terminator</a>, where it halts and detaches from the DNA. As with human DNA-dependent DNA polymerases,&nbsp;<a href="http://en.wikipedia.org/wiki/RNA_polymerase_II" title="RNA polymerase II" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">RNA polymerase II</a>, the enzyme that transcribes most of the genes in the human genome, operates as part of a large&nbsp;<a href="http://en.wikipedia.org/wiki/Protein_complex" title="Protein complex" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">protein complex</a>&nbsp;with multiple regulatory and accessory subunits.<sup id="cite_ref-119" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-119" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[119]</a></sup></p><h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Genetic_recombination"/p> <h2>Genetic recombination</span></h2> 

<table border="0" cellpadding="0" cellspacing="0" style="border-style: solid; border-color: rgb(204, 204, 204); border-style:solid; font-size: 11.199999809265137px; width: 250px; margin: 0.3em;width:250px"> <tbody> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Holliday_Junction.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Holliday Junction.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Holliday_Junction.svg/250px-Holliday_Junction.svg.png" width="250" height="248" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Holliday_Junction.svg/375px-Holliday_Junction.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Holliday_Junction.svg/500px-Holliday_Junction.svg.png 2x" style="border: none; height:248px; vertical-align: middle;width:250px" /></a></td> </tr> <tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Holliday_junction_coloured.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Holliday junction coloured.png" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Holliday_junction_coloured.png/250px-Holliday_junction_coloured.png" width="250" height="250" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/92/Holliday_junction_coloured.png/375px-Holliday_junction_coloured.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/92/Holliday_junction_coloured.png/500px-Holliday_junction_coloured.png 2x" style="border: none; height:250px; vertical-align: middle;width:250px" /></a></td> </tr> </tbody>

<div class="thumbcaption" style="border: none; line-height: 1.4em; font-size: 12px; padding: 3px !important;">Structure of the&nbsp;<a href="http://en.wikipedia.org/wiki/Holliday_junction" title="Holliday junction" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Holliday junction">Holliday junction</a>&nbsp;intermediate in&nbsp;<a href="http://en.wikipedia.org/wiki/Genetic_recombination" title="Genetic recombination" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic recombination">genetic recombination</a>. The four separate DNA strands are coloured red, blue, green and yellow.<sup id="cite_ref-120" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-120" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[120]</a></sup></div>

 <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/Genetic_recombination" title="Genetic recombination" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic recombination">Genetic recombination</a></div> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 252px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:Chromosomal_Recombination.svg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Chromosomal_Recombination.svg/250px-Chromosomal_Recombination.svg.png" widthstyle="250" height="162" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Chromosomal_Recombination.svg/375pxbackground-Chromosomal_Recombination.svg.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Chromosomal_Recombination.svg/500px-Chromosomal_Recombination.svg.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:162px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);250px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:Chromosomal_Recombination.svg" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 402px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:DNA_nanostructures.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/DNA_nanostructures.png/400px-DNA_nanostructures.png" widthstyle="400" height="220" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/55/DNA_nanostructures.png/600pxbackground-DNA_nanostructures.png 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/5/55/DNA_nanostructures.png/800px-DNA_nanostructures.png 2x" style="255); border: 1px solid rgb(204, 204, 204); height:220px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);400px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:DNA_nanostructures.png" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>The DNA structure at left (schematic shown) will self-assemble into the structure visualized by&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Atomic_force_microscope" title="Atomic force microscope" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Atomic force microscope">atomic force microscopy</a>&nbsp;at right.&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_nanotechnology" title="DNA nanotechnology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA nanotechnology">DNA nanotechnology</a>&nbsp;is the field that seeks to design nanoscale structures using the&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_recognition" title="Molecular recognition" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Molecular recognition">molecular recognition</a>&nbsp;properties of DNA molecules. Image from<a rel="nofollow" class="external text" href="http://dx.doi.org/10.1371/journal.pbio.0020073" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Strong, 2004</a>.</div>

 <div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_nanotechnology" title="DNA nanotechnology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA nanotechnology">DNA nanotechnology</a></div> <p style>DNA nanotechnology uses the unique&nbsp;<a href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Molecular_recognition" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;">DNA nanotechnology uses the unique&nbsp;<a href="http://en.wikipedia.org/wiki/Molecular_recognition" title="Molecular recognition" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">molecular recognition>molecular recognition</a>&nbsp;properties of DNA and other nucleic acids to create self-assembling branched DNA complexes with useful properties.<sup id><a href="cite_ref-151" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-151" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[151]</a></sup>&nbsp;DNA is thus used as a structural material rather than as a carrier of biological information. This has led to the creation of two-dimensional periodic lattices (both tile-based as well as using the &quot;<a href="http://en.wikipedia.org/wiki/DNA_origami" title="DNA origami" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="DNA origami">DNA origami</a>&quot; method) as well as three-dimensional structures in the shapes of&nbsp;<a href="http://en.wikipedia.org/wiki/Polyhedron" title="Polyhedron" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Polyhedron">polyhedra</a>.<sup id="cite_ref-152" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-152" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[152]</a></sup>&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_machine" title="DNA machine" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA machine">Nanomechanical devices</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_computing" title="DNA computing" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA computing">algorithmic self-assembly</a>&nbsp;have also been demonstrated,<sup id><a href="cite_ref-153" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://enhttp://en.wikipedia.org/wiki/DNA#cite_note-153" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[153]</a></sup>&nbsp;and these DNA structures have been used to template the arrangement of other molecules such as&nbsp;<a href="http://en.wikipedia.org/wiki/Colloidal_gold" title="Colloidal gold" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Colloidal gold">gold nanoparticles</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Streptavidin" title="Streptavidin" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Streptavidin">streptavidin</a>&nbsp;proteins.<sup id><a href="cite_refhttp://en.wikipedia.org/wiki/DNA#cite_note-154" classstyle="reference" style="linetext-heightdecoration: none; color: 1emrgb(11, 0, 128); unicodebackground-bidiimage: none; white-webkit-isolatespace: nowrap;">[154]</a href="http:></sup></en.wikipedia.orgp> <h3>History and anthropology</wiki/DNA#cite_note-154" styleh3> <div class="textrellink boilerplate further" style="font-decorationstyle: noneitalic; colorpadding-left: rgb(11, 0, 128)1.6em; backgroundmargin-imagebottom: none0.5em; whitefont-family: sans-spaceserif; font-size: 12.800000190734863px; line-height: nowrap19.200000762939453px;">[154]Further information:&nbsp;</a><href="http://en.wikipedia.org/sup><wiki/p><h3 Phylogenetics" style="backgroundtext-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflow: hidden; paddingbackground-topimage: 0.5emnone; padding-bottom: 0.17em" title="Phylogenetics">Phylogenetics</a>&nbsp; border-bottom-style: noneand&nbsp; font-size<a href="http: 16//en.799999237060547px; fontwikipedia.org/wiki/Genetic_genealogy" style="text-familydecoration: sans-serifnone; line-heightcolor: 19.200000762939453pxrgb(11, 0, 128);"><span class="mwbackground-headlineimage: none;" idtitle="History_and_anthropologyGenetic genealogy">History and anthropologyGenetic genealogy</spana></h3div> <div class="rellink boilerplate further" style="font-style: italic; padding-leftp>Because DNA collects mutations over time, which are then inherited, it contains historical information, and, by comparing DNA sequences, geneticists can infer the evolutionary history of organisms, their&nbsp;<a href="http: 1//en.6em; margin-bottom: 0wikipedia.5em; fontorg/wiki/Phylogenetics" style="text-familydecoration: sans-serifnone; font-sizecolor: 12.800000190734863pxrgb(11, 0, 128); linebackground-heightimage: 19.200000762939453pxnone;" title="Phylogenetics">Further information:&nbsp;phylogeny</a>.^{<a href="http://en.wikipedia.org/wiki/Phylogenetics" title="PhylogeneticsDNA#cite_note-155" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"white-space: nowrap;">Phylogenetics[155]</a>&nbsp;and}This field of phylogenetics is a powerful tool in&nbsp;<a href="http://en.wikipedia.org/wiki/Genetic_genealogy" title="Genetic genealogyEvolutionary_biology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Genetic genealogytitle="Evolutionary biology">evolutionary biology</a>. If DNA sequences within a species are compared,&nbsp;</div><p stylea href="marginhttp: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/Population_genetics" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sansrgb(11, 0, 128); background-serif; font-sizeimage: 12.800000190734863pxnone;" title="Population genetics">Because DNA collects mutations over time, which are then inherited, it contains historical information, and, by comparing DNA sequences, geneticists can infer population geneticists</a>&nbsp;can learn the evolutionary history of organisms, theirparticular populations. This can be used in studies ranging from&nbsp;<a href="http://en.wikipedia.org/wiki/PhylogeneticsEcological_genetics" titlestyle="Phylogenetics" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ecological genetics">phylogenyecological genetics</a>.&nbsp;to&nbsp;<sup ida href="cite_ref-155" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-155Anthropology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="Anthropology">[155]anthropology</a></sup>This field of phylogenetics ; For example, DNA evidence is a powerful tool inbeing used to try to identify the&nbsp;<a href="http://en.wikipedia.org/wiki/Evolutionary_biology" title="Evolutionary biologyTen_Lost_Tribes" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Ten Lost Tribes">evolutionary biologyTen Lost Tribes of Israel</a>. If DNA sequences within a species are compared,&nbsp;^{<a href="http://en.wikipedia.org/wiki/Population_genetics" title="Population geneticsDNA#cite_note-156" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">population geneticists[156]</a>&nbsp;can learn the history of particular populations. This can be used in studies ranging from&nbsp;<}^{<a href="http://en.wikipedia.org/wiki/Ecological_genetics" title="Ecological geneticsDNA#cite_note-157" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">ecological genetics[157]</a>&nbsp;to&nbsp;<a href="http:/sup></en.wikipedia.org/wiki/Anthropology" titlep> <p>DNA has also been used to look at modern family relationships, such as establishing family relationships between the descendants of&nbsp;<a href="Anthropology" style="text-decorationhttp: none//en.wikipedia.org/wiki/Sally_Hemings" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Sally Hemings">anthropologySally Hemings</a>&nbsp;and&nbsp; For example, DNA evidence is being used to try to identify the&nbsp;<a href="http://en.wikipedia.org/wiki/Ten_Lost_Tribes" title="Ten Lost TribesThomas_Jefferson" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Thomas Jefferson">Ten Lost Tribes of IsraelThomas Jefferson</a>.<This usage is closely related to the use of DNA in criminal investigations detailed above. Indeed, some criminal investigations have been solved when DNA from crime scenes has matched relatives of the guilty individual.<sup id="cite_ref-156" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-156158" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[156158]</a>}<sup id="cite_ref-157" /p> <h3>Information storage</h3> <div class="referencerellink relarticle mainarticle" style="linefont-heightstyle: 1emitalic; unicodepadding-bidileft: 1.6em; margin-webkitbottom: 0.5em; font-isolate;family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Main article:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA#cite_note-157DNA_digital_data_storage" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;" title="DNA digital data storage">[157]DNA digital data storage</a></supdiv> </p><p style="marginIn a paper published in Nature in January, 2013, scientists from the&nbsp;<a href="http: 0//en.4em 0px 0wikipedia.5em; lineorg/wiki/European_Bioinformatics_Institute" style="text-heightdecoration: 19.200000762939453pxnone; font-familycolor: sans-serifrgb(11, 0, 128); fontbackground-sizeimage: 12.800000190734863pxnone;" title="European Bioinformatics Institute">DNA has also been used to look at modern family relationships, such as establishing family relationships between the descendants ofEuropean Bioinformatics Institute</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Sally_Hemings" title="Sally HemingsAgilent_Technologies" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Agilent Technologies">Sally HemingsAgilent Technologies</a>&nbsp;andproposed a mechanism to use DNA&nbsp#39;<s ability to code information as a href="http://en.wikipedia.org/wiki/Thomas_Jefferson" title="Thomas Jefferson" style="text-decoration: none; color: rgb(11means of digital data storage. The group was able to encode 739 kilobytes of data into DNA code, synthesize the actual DNA, then sequence the DNA and decode the information back to its original form, 0, 128); background-image: none;">Thomas Jefferson</a>with a reported 100% accuracy. The encoded information consisted of text files and audio files. This usage is closely related to the use of DNA in criminal investigations detailed aboveA prior experiment was published in August 2012. Indeed, some criminal investigations have been solved when DNA from crime scenes has matched relatives of the guilty individualIt was conducted by researchers at&nbsp;<a href="http://en.wikipedia.<sup id="cite_ref-158" class="referenceorg/wiki/Harvard_University" style="linetext-heightdecoration: 1emnone; unicodecolor: rgb(11, 0, 128); background-bidiimage: -webkit-isolatenone;" title="Harvard University">Harvard University</a href="http://>, where the text of a 54,000-word book was encoded in DNA.^{<a href="http://en.wikipedia.org/wiki/DNA#cite_note-158159" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[158159]</a>}</psup><h3 stylea href="backgroundhttp://en.wikipedia.org/wiki/DNA#cite_note-160" style="text-imagedecoration: none; margincolor: 0px 0px rgb(11, 0.3em, 128); overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-stylebackground-image: none; fontwhite-sizespace: 16.799999237060547pxnowrap; font-family: sans-serif; line-height: 19.200000762939453px;"">[160]</a><span class="mw-headline" id="Information_storage">Information storage</spansup></h3p> <div class=h2>History of DNA research</h2> <div class="rellink relarticle mainarticleboilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Main articleFurther information:&nbsp;<a href="http://en.wikipedia.org/wiki/DNA_digital_data_storage" title="DNA digital data storageHistory_of_molecular_biology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA digital data storage</a></div><p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In a paper published in Nature in January, 2013, scientists from the&nbsp;<a href="http://en.wikipedia.org/wiki/European_Bioinformatics_Institute" title="European Bioinformatics Institute" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">European Bioinformatics Institute</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Agilent_Technologies" title="Agilent Technologies" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Agilent Technologies</a>&nbsp;proposed a mechanism to use DNA's ability to code information as a means of digital data storage. The group was able to encode 739 kilobytes of data into DNA code, synthesize the actual DNA, then sequence the DNA and decode the information back to its original form, with a reported 100% accuracy. The encoded information consisted of text files and audio files. A prior experiment was published in August 2012. It was conducted by researchers at&nbsp;<a href="http://en.wikipedia.org/wiki/Harvard_University" title="Harvard University" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Harvard University</a>, where the text of a 54,000-word book was encoded in DNA.<sup id="cite_ref-159" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-159" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[159]</a></sup><sup id="cite_ref-160" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-160" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[160]</a></sup></p><h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="History_of_DNA_research">History of DNA research</span></h2><div class="rellink boilerplate further" style="font-style: italic; padding-left: 1.6em; margin-bottom: 0.5em; font-family: sans-serif; font-size: 12.800000190734863px; line-height: 19.200000762939453px;">Further information:&nbsp;<a href="http://en.wikipedia.org/wiki/History_of_molecular_biology" title="History title="History of molecular biology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">History of molecular biology</a></div> 

<div class="thumbinner" style="min-width: 100px; border: 1px solid rgb(204, 204, 204); background-color: rgb(249, 249, 249); font-size: 12px; text-align: center; overflow: hidden; width: 222px; padding: 3px !important;"><a class="image" href="http://en.wikipedia.org/wiki/File:Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="" class="thumbimage" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg/220px-Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg" widthstyle="220" height="173" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_background-_10.1371_journal.pbio.0030341.g001-O.jpg/330px-Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg 1.5xcolor:rgb(255, 255, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg/440px-Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg 2x" style="255); border: 1px solid rgb(204, 204, 204); height:173px; vertical-align: middle; background-colorwidth: rgb(255, 255, 255);220px" /></a> 

<div class="magnify" style="margin-left: 3px; float: right; border: none !important; background-image: none !important;"><a class="internal" href="http://en.wikipedia.org/wiki/File:Maclyn_McCarty_with_Francis_Crick_and_James_D_Watson_-_10.1371_journal.pbio.0030341.g001-O.jpg" class="internal" title="Enlarge" style="text-decoration: none; color: rgb(11, 0, 128); display: block; background-image: none !important; border: none !important;" title="Enlarge"><img alt="" src="http://bits.wikimedia.org/static-1.22wmf12/skins/common/images/magnify-clip.png" width="15" height="11" alt="" style="verticalbackground-alignimage:none !important; border: middlenone !important; display: block; borderheight: none !important11px; backgroundvertical-imagealign: none !importantmiddle;width:15px" /></a></div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">DNA was first isolated by the Swiss physician&nbsp;<a href="http://en.wikipedia.org/wiki/Friedrich_Miescher" title="Friedrich Miescher" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Friedrich Miescher">Friedrich Miescher</a>&nbsp;who, in 1869, discovered a microscopic substance in the pus of discarded surgical bandages. As it resided in the nuclei of cells, he called it &quot;nuclein&quot;.<sup id><a href="cite_ref-161" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-161" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[161]</a></sup>&nbsp;In 1878, Albrecht Kossel isolated the non-protein component of &quot;nuclein&quot;, nucleic acid, and later isolated its five primary&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nucleobases" titlestyle="Nucleobases" class="mwtext-redirect" style="text-decorationdecoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleobases">nucleobases</a>.<sup id="cite_ref-Yale_Jones_1953_162-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Yale_Jones_1953-162" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[162]</a></sup>&nbsp;In 1919, Phoebus Levene identified the base, sugar and phosphate nucleotide unit.<sup id><a href="cite_ref-163" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:/http://en.wikipedia.org/wiki/DNA#cite_note-163" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[163]</a></sup>&nbsp;Levene suggested that DNA consisted of a string of nucleotide units linked together through the phosphate groups. However, Levene thought the chain was short and the bases repeated in a fixed order. In 1937&nbsp;<a href="http://en.wikipedia.org/wiki/William_Astbury" title="William Astbury" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="William Astbury">William Astbury</a>&nbsp;produced the first X-ray diffraction patterns that showed that DNA had a regular structure.<sup id><a href="cite_ref-164" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http:http://en.wikipedia.org/wiki/DNA#cite_note-164" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[164]</a></sup></p> <p style>In 1927,&nbsp;<a href="marginhttp: 0//en.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In 1927,&nbsp;<a href="http://en.wikipediawikipedia.org/wiki/Nikolai_Koltsov" title="Nikolai Koltsov" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Nikolai Koltsov">Nikolai Koltsov</a>&nbsp;proposed that inherited traits would be inherited via a &quot;giant hereditary molecule&quot; made up of &quot;two mirror strands that would replicate in a semi-conservative fashion using each strand as a template&quot;.<sup id="cite_ref-Soyfer_165-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-Soyfer-165" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[165]</a></sup>&nbsp;In 1928,&nbsp;<a href="http://en.wikipedia.org/wiki/Frederick_Griffith" title="Frederick Griffith" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Frederick Griffith">Frederick Griffith</a>&nbsp;discovered that&nbsp;<a hrefclass="httpmw-redirect" href="http://en.wikipedia.org/wiki/Trait_(biology)" title="Trait (biology)" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Trait (biology)">traits</a>&nbsp;of the &quot;smooth&quot; form of&nbsp;<iem>Pneumococcus</iem>&nbsp;could be transferred to the &quot;rough&quot; form of the same bacteria by mixing killed &quot;smooth&quot; bacteria with the live &quot;rough&quot; form.<sup id><a href="cite_ref-166" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.http://en.wikipedia.org/wiki/DNA#cite_note-166" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[166]</a></sup>&nbsp;This system provided the first clear suggestion that DNA carries genetic information&mdash;the&nbsp;<a href="http://en.wikipedia.org/wiki/Avery%E2%80%93MacLeod%E2%80%93McCarty_experiment" title="Avery&ndash;MacLeod&ndash;McCarty experiment" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Averytitle="Avery–MacLeod–McCarty experiment">Avery&ndash;MacLeod&ndash;McCarty experiment</a>&mdash;when&nbsp;<a href="http://en.wikipedia.org/wiki/Oswald_Avery" title="Oswald Avery" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Oswald Avery">Oswald Avery</a>, along with coworkers&nbsp;<a href="http://en.wikipedia.org/wiki/Colin_Munro_MacLeod" title="Colin Munro MacLeod" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Colin Munro MacLeod">Colin MacLeod</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Maclyn_McCarty" title="Maclyn McCarty" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Maclyn McCarty">Maclyn McCarty</a>, identified DNA as the&nbsp;<a href="http://en.wikipedia.org/wiki/Griffith%27s_experiment" title="Griffith's experiment" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Griffith's experiment">transforming principle</a>&nbsp;in 1943.<sup id="cite_ref-167" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-167" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[167]</a></sup>&nbsp;DNA'&#39;s role in&nbsp;<a href="http://en.wikipedia.org/wiki/Heredity" title="Heredity" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Heredity">heredity</a>&nbsp;was confirmed in 1952, when&nbsp;<a href="http://en.wikipedia.org/wiki/Alfred_Hershey" title="Alfred Hershey" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Alfred Hershey">Alfred Hershey</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Martha_Chase" title="Martha Chase" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Martha Chase">Martha Chase</a>&nbsp;in the&nbsp;<a href="http://en.wikipedia.org/wiki/Hershey%E2%80%93Chase_experiment" title="Hershey&ndash;Chase experiment" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Hershey–Chase experiment">Hershey&ndash;Chase experiment</a>&nbsp;showed that DNA is the&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Genetic_material" title="Genetic material" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic material">genetic material</a>&nbsp;of the&nbsp;<a href="http://en.wikipedia.org/wiki/Enterobacteria_phage_T2" title="Enterobacteria phage T2" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Enterobacteria phage T2">T2 phage</a>.<sup id="cite_ref-168" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-168" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[168]</a></sup></p> <p style>In 1953,&nbsp;<a href="marginhttp: 0//en.4em 0px 0wikipedia.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In 1953,&nbsp;<a href="http://en.wikipedia.orgorg/wiki/James_Watson" title="James Watson" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="James Watson">James Watson</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Francis_Crick" title="Francis Crick" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Francis Crick">Francis Crick</a>&nbsp;suggested what is now accepted as the first correct double-helix model of&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Molecular_structure_of_Nucleic_Acids" title="Molecular structure of Nucleic Acids" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">DNA title="Molecular structure of Nucleic Acids">DNA structure</a>&nbsp;in the journal&nbsp;<iem><a href="http://en.wikipedia.org/wiki/Nature_(journal)" title="Nature (journal)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nature (journal)">Nature</a></iem>.<sup id><a href="cite_ref-FWPUB_5-2" class="reference" style="line-heighthttp: 1em; unicode-bidi: -webkit-isolate;"><a href="http:////en.wikipedia.org/wiki/DNA#cite_note-FWPUB-5" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[5]</a></sup>&nbsp;Their double-helix, molecular model of DNA was then based on a single&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/X-ray_diffraction" title="X-ray diffraction" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="X-ray diffraction<">X-ray diffraction</a>&nbsp;image (labeled as &quot;<a href="http://en.wikipedia.org/wiki/Photo_51" title="Photo 51" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Photo 51">Photo 51</a>&quot;)<sup id="cite_ref-169" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-169" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[169]</a></sup>&nbsp;taken by&nbsp;<a href="http://en.wikipedia.org/wiki/Rosalind_Franklin" titlestyle="Rosalind Franklin" style="text-text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Rosalind Franklin">Rosalind Franklin</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Raymond_Gosling" title="Raymond Gosling" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Raymond Gosling">Raymond Gosling</a>&nbsp;in May 1952, as well as the information that the DNA bases are paired&nbsp;&mdash; also obtained through private communications from Erwin Chargaff in the previous years.&nbsp;<a href="http://en.wikipedia.org/wiki/Chargaff%27s_rules" title="Chargaff's rules" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Chargaff's rules</a">Chargaff&nbsp#39;s rules</a>&nbsp;played a very important role in establishing double-helix configurations for B-DNA as well as A-DNA.</p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">Experimental evidence supporting the Watson and Crick model was published in a series of five articles in the same issue of&nbsp;<iem>Nature</iem>.<sup id><a href="cite_ref-NatureDNA50_170-0" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://http://en.wikipedia.org/wiki/DNA#cite_note-NatureDNA50-170" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[170]</a></sup>&nbsp;Of these, Franklin and Gosling'&#39;s paper was the first publication of their own X-ray diffraction data and original analysis method that partially supported the Watson and Crick model;<sup id><a href="cite_ref-NatFranGos_41-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://enhttp://en.wikipedia.org/wiki/DNA#cite_note-NatFranGos-41" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[41]</a></sup><sup id><a href="cite_ref-171" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_notehttp://en.wikipedia.org/wiki/DNA#cite_note-171" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[171]</a></sup>&nbsp;this issue also contained an article on DNA structure by&nbsp;<a href="http://en.wikipedia.org/wiki/Maurice_Wilkins" titlestyle="Maurice Wilkins" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Maurice Wilkins">Maurice Wilkins</a>&nbsp;and two of his colleagues, whose analysis and&nbsp;<iem>in vivo</iem>&nbsp;B-DNA X-ray patterns also supported the presence&nbsp;<iem>in vivo</iem>&nbsp;of the double-helical DNA configurations as proposed by Crick and Watson for their double-helix molecular model of DNA in the previous two pages of&nbsp;<iem>Nature</iem>.<sup id="cite_ref-NatWilk_42-1" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-NatWilk-42" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[42]</a></sup>&nbsp;In 1962, after Franklin'&#39;s death, Watson, Crick, and Wilkins jointly received the Nobel Prize in&nbsp;<a href="http://en.wikipedia.org/wiki/Nobel_Prize_in_Physiology_or_Medicine" titlestyle="Nobel Prize in Physiology or Medicine" style="text-decorationtext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nobel Prize in Physiology or Medicine">Physiology or Medicine</a>.<sup id="cite_ref-172" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-172" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[172]</a></sup>&nbsp;Nobel Prizes were awarded only to living recipients at the time. A debate continues about who should receive credit for the discovery.<sup id="cite_ref-173" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;">><a href="http://en.wikipedia.org/wiki/DNA#cite_note-173" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[173]</a></sup></p> <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">In an influential presentation in 1957, Crick laid out the&nbsp;<a href="http://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology" title="Central dogma of molecular biology" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Central dogma of molecular biology">central dogma of molecular biology</a>, which foretold the relationship between DNA, RNA, and proteins, and articulated the &quot;adaptor hypothesis&quot;.<sup id="cite_ref-174" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-174" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[174]</a></sup>&nbsp;Final confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 through the Meselson&ndash;Stahl experiment.<sup id><a href="cite_ref-175" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="httphttp://en.wikipedia.org/wiki/DNA#cite_note-175" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[175]</a></sup>&nbsp;Further work by Crick and coworkers showed that the genetic code was based on non-overlapping triplets of bases, called codons, allowing&nbsp;<a href="http://en.wikipedia.org/wiki/Har_Gobind_Khorana" title="Har Gobind Khorana" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Har Gobind Khorana">Har Gobind Khorana</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Robert_W._Holley" titlestyle="Robert W. Holley" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Robert W. Holley">Robert W. Holley</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Marshall_Warren_Nirenberg" title="Marshall Warren Nirenberg" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Marshall Warren Nirenberg">Marshall Warren Nirenberg</a>&nbsp;to decipher the genetic code.<sup id="cite_ref-176" class="reference" style="line-height: 1em; unicode-bidi: -webkit-isolate;"><a href="http://en.wikipedia.org/wiki/DNA#cite_note-176" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none; white-space: nowrap;">[176]</a></sup>&nbsp;These findings represent the birth of molecular biology.</p> 

 <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="See_also">See also</span></h2> 

<table style="font-size: 11.199999809265137px; background-color: rgb(249, 249, 249); font-size:11.199999809265137px; line-height: 12px; max-width: 175px;"> <tbody> <tr valign="middle"> <td style="text-align: center;"><a class="image" href="http://en.wikipedia.org/wiki/File:TPI1_structure.png" class="image" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;"><img alt="Portal icon" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/TPI1_structure.png/32px-TPI1_structure.png" width="32" height="20" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/TPI1_structure.png/48px-TPI1_structure.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/TPI1_structure.png/64px-TPI1_structure.png 2x" style="border: none; height:20px; vertical-align: middle;width:32px" /></a></td> <td style="padding: 0px 0.2em; vertical-align: middle; font-style: italic; font-weight: bold;"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Portal:Molecular_and_Cellular_Biology" title="Portal:Molecular and Cellular Biology" class="mw-redirect" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Portal:Molecular and Cellular Biology">Molecular and Cellular Biology portal</a></td> </tr> </tbody>

<ul style="line-height: 1.5em; margin: 0.3em 0px 0px 1.6em; padding: 0px; list-style-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAANAQMAAABb8jbLAAAABlBMVEX///8AUow5QSOjAAAAAXRSTlMAQObYZgAAABNJREFUCB1jYEABBQw/wLCAgQEAGpIDyT0IVcsAAAAASUVORK5CYII=);"> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Autosome" title="Autosome" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Autosome">Autosome</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Crystallography" title="Crystallography" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Crystallography">Crystallography</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/DNA-encoded_chemical_library" title="DNA-encoded chemical library" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA-encoded chemical library">DNA-encoded chemical library</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/DNA_microarray" title="DNA microarray" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA microarray">DNA microarray</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/DNA_sequencing" title="DNA sequencing" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="DNA sequencing">DNA sequencing</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Genetic_disorder" title="Genetic disorder" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Genetic disorder">Genetic disorder</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Haplotype" title="Haplotype" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Haplotype">Haplotype</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/List_of_nucleic_acid_simulation_software" title="List of nucleic acid simulation software" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="List of nucleic acid simulation software">List of nucleic acid simulation software</a>- Nucleic acid modeling</li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Meiosis" title="Meiosis" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Meiosis">Meiosis</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Nucleic_acid_double_helix" title="Nucleic acid double helix" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleic acid double helix">Nucleic acid double helix</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Nucleic_acid_notation" title="Nucleic acid notation" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nucleic acid notation">Nucleic acid notation</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Phosphoramidite" title="Phosphoramidite" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Phosphoramidite">Phosphoramidite</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Southern_blot" title="Southern blot" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Southern blot">Southern blot</a></li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/X-ray_scattering_techniques" title="X-ray scattering techniques" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="X-ray scattering techniques">X-ray scattering techniques</a></li> <li style="margin-bottom: 0.1em;"><iem><a href="http://en.wikipedia.org/wiki/Proteopedia" title="Proteopedia" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Proteopedia">Proteopedia</a>&nbsp;<a rel="nofollow" class="external text" href="http://www.proteopedia.org/wiki/index.php/DNA" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA</a></iem></li>

 <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="References">References</span></h2> 

 <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="Further_reading">Further reading</span></h2> 

<ul style> <li>Berry, Andrew;&nbsp;<a href="line-heighthttp: 1//en.5em; margin: 0wikipedia.3em 0px 0px 1.6em; paddingorg/wiki/James_Watson" style="text-decoration: 0pxnone; list-style-imagecolor: urlrgb(data:image/png;base6411, 0,iVBORw0KGgoAAAANSUhEUgAAAAUAAAANAQMAAABb8jbLAAAABlBMVEX///8AUow5QSOjAAAAAXRSTlMAQObYZgAAABNJREFUCB1jYEABBQw/wLCAgQEAGpIDyT0IVcsAAAAASUVORK5CYII=128); background-image: none;"> <li styletitle="margin-bottom: 0.1em;James Watson"><span class="citation book" style="word-wrap: break-word;">BerryWatson, Andrew;&nbsp;James</a>. (2003).&nbsp;<em>DNA: the secret of life</em>. New York: Alfred A. Knopf.&nbsp;<a href="http://en.wikipedia.org/wiki/James_WatsonInternational_Standard_Book_Number" title="James Watson" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">Watson, JamesISBN</a>. (2003).&nbsp;<i>DNAa href="http: the secret of life</i>. New York: Alfred A. Knopf.&nbsp;<a href="http:////en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book NumberSpecial:BookSources/0-375-41546-7" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Special:BookSources/0-375-41546-7">ISBN0-375-41546-7</a>&nbsp;.<a href="http://enli> <li>Calladine, Chris R.wikipedia; Drew, Horace R.org/wiki; Luisi, Ben F. and Travers, Andrew A. (2003).&nbsp;<em>Understanding DNA: the molecule &amp; how it works</Specialem>. Amsterdam:BookSources/0-375-41546-7" titleElsevier Academic Press.&nbsp;<a href="Specialhttp:BookSources/0-375-41546-7/en.wikipedia.org/wiki/International_Standard_Book_Number" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">0-375-41546-7ISBN</a>.&nbsp;<a href="http:/span></li> <li style="margin-bottomen.wikipedia.org/wiki/Special: BookSources/0.1em;"><span class="citation book-12-155089-3" style="wordtext-wrapdecoration: break-wordnone;">Calladinecolor: rgb(11, Chris R.; Drew0, Horace R.; Luisi, Ben F. and Travers, Andrew A. (2003128).&nbsp;<i>Understanding DNAbackground-image: the molecule &ampnone; how it works</i>. Amsterdam: Elsevier Academic Press.&nbsp;<a href" title="httpSpecial:BookSources/0-12-155089-3">0-12-155089-3</ena>.wikipedia.org</wiki/International_Standard_Book_Number" title="International Standard Book Number" style="text-decoration: noneli> <li>Dennis, Carina; color: rgbJulie Clayton (11, 0, 1282003).&nbsp; background-image: none;">ISBN<em>50 years of DNA</aem>. Basingstoke: Palgrave Macmillan.&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0-12-155089-3International_Standard_Book_Number" titlestyle="Special:BookSources/0-12-155089-3" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">0-12-155089-3ISBN</a>.&nbsp;<a href="http://en.wikipedia.org/span><wiki/Special:BookSources/li> <li 1-4039-1479-6" style="margintext-bottomdecoration: none; color: rgb(11, 0.1em, 128); background-image: none;"><span classtitle="citation book" style="wordSpecial:BookSources/1-wrap: break4039-word;"1479-6">Dennis, Carina; Julie Clayton (2003).&nbsp;1-4039-1479-6<i/a>50 years of DNA.</ili> <li>. Basingstoke: Palgrave Macmillan.&nbsp;<a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book NumberHorace_Freeland_Judson" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Horace Freeland Judson">ISBNJudson, Horace F</a>. 1979.&nbsp;<em>The Eighth Day of Creation: Makers of the Revolution in Biology</em>. Touchstone Books,&nbsp;<a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/1-4039-1479-6" title="Special:BookSources/1-4039-1479-60671225405" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">1ISBN 0-4039671-147922540-65</a>.2nd edition: Cold Spring Harbor Laboratory Press, 1996 paperback:&nbsp;</span></li> <li stylea class="margininternal mw-magiclink-bottom: 0.1em;isbn"><a href="http://en.wikipedia.org/wiki/Horace_Freeland_Judson" title="Horace Freeland JudsonSpecial:BookSources/0879694785" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Judson, Horace FISBN 0-87969-478-5</a>. 1979.&nbsp;<i/li>The Eighth Day of Creation: Makers of the Revolution in Biology</i <li>. Touchstone Books,&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0671225405Robert_Olby" classstyle="internal mwtext-magiclink-isbn" style="text-decoration: decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Robert Olby">ISBN 0-671-22540-5Olby, Robert C.</a>&nbsp;(1994). 2nd edition&nbsp;<em>The path to the double helix: Cold Spring Harbor Laboratory Press, 1996 paperbackthe discovery of DNA</em>. New York:Dover Publications.&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0879694785" class="internal mw-magiclink-isbnInternational_Standard_Book_Number" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">ISBN 0-87969-478-5</a>.&nbsp;</li> <li style="margin-bottom: 0.1em;"><span class="citation book" style="word-wrap: break-word;"><a a href="http://en.wikipedia.org/wiki/Robert_Olby" title="Robert OlbySpecial:BookSources/0-486-68117-3" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Olby, Robert C.<title="Special:BookSources/a0-486-68117-3">&nbsp;(1994).&nbsp;<i>The path to the double helix: the discovery of DNA0-486-68117-3</ia>. New York: Dover Publications.&nbsp, first published in October 1974 by MacMillan, with foreword by Francis Crick;<the definitive DNA textbook,revised in 1994 with a href="http:9 page postscript<//enli> <li>Micklas, David.wikipedia2003.org&nbsp;<em>DNA Science: A First Course</wiki/International_Standard_Book_Number" titleem>. Cold Spring Harbor Press:&nbsp;<a class="International Standard Book Numberinternal mw-magiclink-isbn" stylehref="text-decorationhttp: none; color//en.wikipedia.org/wiki/Special:BookSources/9780879696368" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN978-0-87969-636-8</a>&nbsp;</li> <li><a href="http://en.wikipedia.org/wiki/Special:BookSources/0-486-68117-3" title="Special:BookSources/0-486-68117-3Matt_Ridley" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Matt Ridley">0-486-68117-3Ridley, Matt</a>&nbsp;(2006).&nbsp;<em>Francis Crick: discoverer of the genetic code</spanem>. Ashland, first published in October 1974 by MacMillanOH: Eminent Lives, with foreword by Francis CrickAtlas Books.&nbsp;the definitive DNA textbook,revised in 1994 with <a 9 page postscript<href="http://en.wikipedia.org/wiki/li> <li International_Standard_Book_Number" style="margintext-bottomdecoration: 0.1emnone;">Micklascolor: rgb(11, 0, David. 2003.&nbsp128); background-image: none;<i" title="International Standard Book Number">DNA Science: A First CourseISBN</ia>. Cold Spring Harbor Press:&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/9780879696368" class="internal mw0-06-magiclink082333-isbnX" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN 978-title="Special:BookSources/0-8796906-636082333-8X">0-06-082333-X</a>.</li> <li style="margin-bottom: 0>Olby, Robert C. (2009).1em&nbsp;"<em><span class="citation book" style="word-wrapFrancis Crick: A Biography</em>. Plainview, N.Y: break-wordCold Spring Harbor Laboratory Press.&nbsp;"><a href="http://en.wikipedia.org/wiki/Matt_RidleyInternational_Standard_Book_Number" titlestyle="Matt Ridley" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">Ridley, MattISBN</a>&nbsp;(2006).&nbsp;<i>Francis Cricka href="http: discoverer of the genetic code</i>. Ashland, OH: Eminent Lives, Atlas Books.&nbsp;<a href="http:///en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book NumberSpecial:BookSources/0-87969-798-9" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN</a>&nbsp;<a hreftitle="httpSpecial:BookSources//en.wikipedia.org/wiki/Special:BookSources/00-87969-06798-082333-X9" title="Special:BookSources/>0-0687969-082333798-X" style="text-decoration: none9</a>.</li> <li>Rosenfeld, Israel. 2010.&nbsp; color<em>DNA: rgb(11, 0, 128); background-image: none;">0-06-082333-XA Graphic Guide to the Molecule that Shook the World</aem>.</span></li> <li style="margin-bottomColumbia University Press: 0.1em&nbsp;"><span a class="citation bookinternal mw-magiclink-isbn" stylehref="word-wraphttp: break-word;">Olby, Robert C//en. (2009)wikipedia.&nbsp;<i>Francis Crickorg/wiki/Special: A Biography<BookSources/i>. Plainview, N.Y9780231142717" style="text-decoration: Cold Spring Harbor Laboratory Press.&nbspnone;<a href="httpcolor://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number" style="text-decoration: none; color: rgb(11, rgb(11, 0, 128); background-image: none;">ISBN978-0-231-14271-7</a>&nbsp;</a href="http:><//enli> <li>Schultz, Mark and Zander Cannon.wikipedia2009.org&nbsp;<em>The Stuff of Life: A Graphic Guide to Genetics and DNA</wiki/Specialem>. Hill and Wang:BookSources/0-87969-798-9&nbsp;<a class="internal mw-magiclink-isbn" titlehref="http://en.wikipedia.org/wiki/Special:BookSources/0-87969-798-90809089475" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN 0-879698090-7988947-95</a>.</spanli> </li> <li a href="http://en.wikipedia.org/wiki/Gunther_Stent" style="margintext-bottomdecoration: 0.1emnone; color: rgb(11, 0, 128); background-image: none;" title="Gunther Stent">RosenfeldStent, Israel. 2010.&nbsp;Gunther Siegmund<i>DNA: A Graphic Guide to the Molecule that Shook the World</i/a>; Watson, James. (1980). Columbia University Press:&nbsp;<em><a href="http://en.wikipedia.org/wiki/Special:BookSources/9780231142717" class="internal mw-magiclink-isbn" styleThe_Double_Helix" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="The Double Helix">ISBN 978-0-231-14271-7The double helix: a personal account of the discovery of the structure of DNA</a></liem> . New York: Norton.&nbsp;<li stylea href="margin-bottomhttp: 0//en.1em;wikipedia.org/wiki/International_Standard_Book_Number" style=">Schultz, Mark and Zander Cannon. 2009.&nbsptext-decoration: none;<i>The Stuff of Lifecolor: A Graphic Guide to Genetics and DNA</i>. Hill and Wangrgb(11, 0, 128); background-image:&nbspnone;<a href" title="httpInternational Standard Book Number">ISBN</a>&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0809089475" class="internal mw0-393-magiclink95075-isbn1" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN title="Special:BookSources/0-393-95075-1">0-8090393-894795075-51</a>.</li> <li style="margin-bottom: 0>Watson, James.1em;">2004.&nbsp;<em>DNA: The Secret of Life<span /em>. Random House:&nbsp;<a class="citation bookinternal mw-magiclink-isbn" stylehref="word-wrap: break-word;"><a href="httphttp:///en.wikipedia.org/wiki/Gunther_Stent" title="Gunther StentSpecial:BookSources/9780099451846" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Stent, Gunther Siegmund<ISBN 978-0-09-945184-6</a>; Watson, James. (1980).&nbsp;<i/li> <li><a href="http://en.wikipedia.org/wiki/The_Double_Helix" title="The Double HelixMaurice_Wilkins" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">The double helix: a personal account of the discovery of the structure of DNAtitle="Maurice Wilkins">Wilkins, Maurice</a></i>. New York: Norton.&nbsp;<(2003).&nbsp;<em>The third man of the double helix the autobiography of Maurice Wilkins</em>. Cambridge, Eng: University Press.&nbsp;<a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="International Standard Book Number">ISBN</a>&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0-39319-95075860665-1" title="Special:BookSources/0-393-95075-1" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">0-393-95075-1</a>.</span></li> <li style="margin-bottom: 0.1em;">Watson, James. 2004.&nbsp;<i>DNA: The Secret of Life</i>. Random House:&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/9780099451846" class="internal mw-magiclink-isbn" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN 978-0-09-945184-6</a></li> <li style="margin-bottom: 0.1em;"><span class="citation book" style="word-wrap: break-word;"><a href="http://en.wikipedia.org/wiki/Maurice_Wilkins" title="Maurice Wilkins" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">Wilkins, Maurice</a>&nbsp;(2003).&nbsp;<i>The third man of the double helix the autobiography of Maurice Wilkins</i>. Cambridge, Eng: University Press.&nbsp;<a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number6" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">ISBN</a>&nbsp;<a href="http://en.wikipedia.org/wiki/Special:BookSources/0-19-860665-6" title="Special:BookSources/0-19-860665-6" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">0-19-860665-6</a>.</span></li>

 <h2 style="background-image: none; font-weight: normal; margin: 0px 0px 0.6em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(170, 170, 170); font-size: 19.200000762939453px; font-family: sans-serif; line-height: 19.200000762939453px;"><span class="mw-headline" id="External_links">External links</span></h2> <table classcellpadding="vertical-navbox nowraplinks infobox bordered0" cellspacing="5" cellpaddingclass="0bordered infobox nowraplinks vertical-navbox" style="background-color:rgb(249, 249, 249); border-stylecollapse: solidcollapse; border-color: rgb(170, 170, 170); fontborder-sizespacing: 110.199999809265137px4em 0px; backgroundborder-colorstyle:solid; clear: rgb(249, 249, 249)right; color: rgb(0, 0, 0); margin: 0px 0px 1em 1em; padding: 0.2em; float: right; clearfont-family: rightsans-serif; textfont-alignsize: center11.199999809265137px; line-height: 1.4em; border-collapsemargin:0px 0px 1em 1em; padding: collapse0.2em; fonttext-familyalign: sans-serifcenter; width: auto; border-spacing: 0.4em 0px;"> <tbody> <tr> <th style="borderbackground-stylecolor: solidrgb(239, 239, 239); border-color: rgb(170, 170, 170); vertical-align: top; padding: 0.2em 0.4em; line-height: 1.2em; background-color: rgb(239, 239, 239); font-size: 1em;">Library resources</th> </tr> <tr> <th style="border-style: solid; border-color: rgb(170, 170, 170); vertical-align: top; padding: 0.1em;">About DNA</th> </tr> <tr> <td class="plainlist" style="border-style: solid; border-color: rgb(170, 170, 170); vertical-align: top; padding: 0px 0.1em 0.4em;"> <ul style="line-height: inherit; list-style: none none; margin: 0px; padding: 0px;"> <li style="margin-bottom: 0px;"><a class="external text" href="http://tools.wmflabs.org/ftl/cgi-bin/ftl?st=&amp;su=DNA&amp;library=OLBP" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); white-space: nowrap; padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Online books</a></li> <li style="margin-bottom: 0px;"><a class="external text" href="http://tools.wmflabs.org/ftl/cgi-bin/ftl?st=&amp;su=DNA" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); white-space: nowrap; padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Resources in your library</a></li> <li style="margin-bottom: 0px;"><a class="external text" href="http://tools.wmflabs.org/ftl/cgi-bin/ftl?st=&amp;su=DNA&amp;library=0CHOOSE0" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); white-space: nowrap; padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Resources in other libraries</a></li> </ul> </td> </tr> </tbody>

 <table class="metadata mbox-small metadata plainlinks" style="borderbackground-stylecolor: solidrgb(249, 249, 249); border-color: rgb(170, 170, 170); fontborder-sizestyle: 11.199999809265137pxsolid; clear: right; float: right; margin: 4px 0px 4px 1em; width: 238px; line-height: 1.25em; color: rgb(0, 0, 0); float:right; font-family: sans-serif; backgroundfont-size:11.199999809265137px; line-colorheight:1.25em; margin: rgb(249, 249, 249)4px 0px 4px 1em;width:238px"> <tbody> <tr> <td class="mbox-image" style="border: none; padding: 2px 0px 2px 0.9em; text-align: center;"><img alt="" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Wikiquote-logo-en.svg/40px-Wikiquote-logo-en.svg.png" width="40" height="40" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Wikiquote-logo-en.svg/60px-Wikiquote-logo-en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Wikiquote-logo-en.svg/80px-Wikiquote-logo-en.svg.png 2x" style="border: none; height:40px; vertical-align: middle;width:40px" /></td> <td class="mbox-text plainlist" style="border: none; padding: 0.25em 0.9em; width: 161.3249969482422px;">Wikiquote has a collection of quotations related to:&nbsp;<iem><bstrong><a class="extiw" href="http://en.wikiquote.org/wiki/Special:Search/DNA" class="extiw" title="q:Special:Search/DNA" style="text-decoration: none; color: rgb(102, 51, 102); background-image: none !important; padding: 0px !important;" title="q:Special:Search/DNA">DNA</a></bstrong></iem></td> </tr> </tbody>

 <table class="metadata mbox-small metadata plainlinks" style="borderbackground-stylecolor: solidrgb(249, 249, 249); border-color: rgb(170, 170, 170); fontborder-sizestyle: 11.199999809265137pxsolid; clear: right; float: right; margin: 4px 0px 4px 1em; width: 238px; line-height: 1.25em; color: rgb(0, 0, 0); float:right; font-family: sans-serif; backgroundfont-size:11.199999809265137px; line-colorheight:1.25em; margin: rgb(249, 249, 249)4px 0px 4px 1em;width:238px"> <tbody> <tr> <td class="mbox-image" style="border: none; padding: 2px 0px 2px 0.9em; text-align: center;"><img alt="" src="http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" width="30" height="40" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" style="border: none; height:40px; vertical-align: middle;width:30px" /></td> <td class="mbox-text plainlist" style="border: none; padding: 0.25em 0.9em; width: 170.9250030517578px;">Wikimedia Commons has media related to:&nbsp;<iem><bstrong><a class="extiw" href="http://commons.wikimedia.org/wiki/Category:DNA" class="extiw" title="commons:Category:DNA" style="text-decoration: none; color: rgb(102, 51, 102); background-image: none !important; padding: 0px !important;" title="commons:Category:DNA">DNA</a></bstrong></iem></td> </tr> </tbody>

 <div id="section_SpokenWikipedia" class="infobox sisterproject plainlinks haudio" id="section_SpokenWikipedia" style="border: 1px solid rgb(170, 170, 170); background-color: rgb(249, 249, 249); margin: 0.5em 0px 0.5em 1em; padding: 0.2em; float: right; clear: right; font-size: 11.199999809265137px; line-height: 1.5em; width: 20em; font-family: sans-serif;"><div style="text-align: center; white-space: nowrap;"><bstrong>Listen to this article</bstrong>&nbsp;(<a href="http://en.wikipedia.org/wiki/File:Dna.ogg" title="File:Dna.ogg" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none !important; padding: 0px !important;" title="File:Dna.ogg">info/dl</a>) 

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 <div style="font-size: xx-small; line-height: 1.6em; margin-left: 60px;">This audio file was created from a revision of the &quot;<span class="fn">DNA</span>&quot; article dated 2007-02-12, and does not reflect subsequent edits to the article. (<a href="http://en.wikipedia.org/wiki/Wikipedia:Media_help" title="Wikipedia:Media help" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none !important; padding: 0px !important;" title="Wikipedia:Media help">Audio help</a>)</div> <div style="text-align: center; clear: both;"><bstrong><a href="http://en.wikipedia.org/wiki/Wikipedia:Spoken_articles" title="Wikipedia:Spoken articles" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none !important; padding: 0px !important;" title="Wikipedia:Spoken articles">More spoken articles</a></bstrong></div>

 <p style="margin: 0.4em 0px 0.5em; line-height: 19.200000762939453px; font-family: sans-serif; font-size: 12.800000190734863px;">&nbsp;</p> <ul style> <li><a class="line-height: 19.200000762939453px; marginexternal text" href="http: 0//www.3em 0px 0px 1dmoz.6em; padding: 0px; list-style-image: url(data:imageorg/Science/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAANAQMAAABb8jbLAAAABlBMVEXBiology/Biochemistry_and_Molecular_Biology/Biomolecules/Nucleic_Acids/DNA/8AUow5QSOjAAAAAXRSTlMAQObYZgAAABNJREFUCB1jYEABBQw/wLCAgQEAGpIDyT0IVcsAAAAASUVORK5CYII=); font-family: sans-serif; font-size: 12.800000190734863px;"> <li style="margin-bottom: 0.1em;"><a rel="nofollow" classstyle="external text" href="http-decoration://www.dmoz.org/Science/Biology/Biochemistry_and_Molecular_Biology/Biomolecules/Nucleic_Acids/DNA//" style="text-decoration: none; none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA</a>&nbsp;at the&nbsp;<a href="http://en.wikipedia.org/wiki/Open_Directory_Project" title="Open Directory Project" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Open Directory Project">Open Directory Project</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://pipe.scs.fsu.edu/displar.html" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA binding site prediction on protein</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://nobelprize.org/educational_games/medicine/dna_double_helix/" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA the Double Helix Game</a>&nbsp;From the official Nobel Prize web site</li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.fidelitysystems.com/Unlinked_DNA.html" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA under electron microscope</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.dnalc.org/" stylerel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Dolan DNA Learning Center</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.nature.com/nature/dna50/archive.html" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Double Helix: 50 years of DNA</a>,&nbsp;<iem><a href="http://en.wikipedia.org/wiki/Nature_(journal)" title="Nature (journal)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nature (journal)">Nature</a></iem></li> <li style="margin-bottom: 0.1em;">><iem><a href="http://en.wikipedia.org/wiki/Proteopedia" title="Proteopedia" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Proteopedia">Proteopedia</a>&nbsp;<a rel="nofollow" class="external text" href="http://www.proteopedia.org/wiki/index.php/DNA" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA</a></iem></li> <li style="margin-bottom: 0.1em;"><iem><a href="http://en.wikipedia.org/wiki/Proteopedia" title="Proteopedia" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Proteopedia">Proteopedia</a>&nbsp;<a rel="nofollow" class="external text" href="http://www.proteopedia.org/wiki/index.php/Forms_of_DNA" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Forms_of_DNA</a></iem></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.nature.com/encode/" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">ENCODE threads explorer</a>&nbsp;ENCODE Home page.&nbsp;<a href="http://en.wikipedia.org/wiki/Nature_(journal)" title="Nature (journal)" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Nature (journal)">Nature (journal)</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.ncbe.reading.ac.uk/DNA50/" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Double Helix 1953&ndash;2003</a>&nbsp;National Centre for Biotechnology Education</li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class><a class="external text" href="http://www.genome.gov/10506718" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Genetic Education Modules for Teachers</a>&mdash;<iem>DNA from the Beginning</iem>&nbsp;Study Guide</li> <li style="margin-bottom: 0.1em;"><a href="http://en.wikipedia.org/wiki/Protein_Data_Bank" title="Protein Data Bank" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;">title="Protein Data Bank">PDB Molecule of the Month</a>&nbsp;<iem><a rel="nofollow" class="external text" href="http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb23_1.html" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">pdb23_1</a></iem></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://mason.gmu.edu/~emoody/rfranklin.html" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Rosalind Franklin'&#39;s contributions to the study of DNA</a></li> <li style="margin-bottom: 0.1em;">><a rel="nofollow" class="external text" href="http://www.genome.gov/10506367" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">U.S. National DNA Day</a>&mdash;watch videos and participate in real-time chat with top scientists</li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.nytimes.com/packages/pdf/science/dna-article.pdf" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(http://upload.wikimedia.org/wikipedia/commons/2/23/Icons-mini-file_acrobat.gif); padding-right: 18px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Clue to chemistry of heredity found</a>&nbsp;<a href="http://en.wikipedia.org/wiki/The_New_York_Times" title="The New York Times" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="The New York Times">The New York Times</a>&nbsp;June 1953. First American newspaper coverage of the discovery of the DNA structure</li> <li style><a href="margin-bottomhttp: 0//en.wikipedia.1em;org/wiki/Robert_Olby"><span class="citation journal" style="word-wrap: break-word;"><a href="http://en.wikipedia.org/wiki/Robert_Olby" title="Robert Olby" stylestyle="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Robert Olby">Olby R</a>&nbsp;(2003). &quot;Quiet debut for the double helix&quot;.&nbsp;<iem>Nature</iem>&nbsp;<bstrong>421</bstrong>&nbsp;(6921): 402&ndash;5.&nbsp;<a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="http://dx.doi.org/10.1038%2Fnature01397" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">10.1038/nature01397</a>.&nbsp;<a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" titlestyle="PubMed Identifier" class="mw-redirect" style="texttext-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="PubMed Identifier">PMID</a>&nbsp;<a rel="nofollow" class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/12540907" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">12540907</a>.</spanli> </li> <li stylea class="margin-bottom: 0.1em;"><a rel="nofollow" class="external textexternal text" href="http://www.dnaftb.org/" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">DNA from the Beginning</a>&nbsp;Another DNA Learning Center site on DNA, genes, and heredity from Mendel to the human genome project.</li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://orpheus.ucsd.edu/speccoll/testing/html/mss0660a.html#abstract" stylerel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">The Register of Francis Crick Personal Papers 1938&nbsp;&ndash; 2007</a>&nbsp;at Mandeville Special Collections Library,&nbsp;<a href="http://en.wikipedia.org/wiki/University_of_California,_San_Diego" title="University of California, San Diego" style="text-decoration: none; color: rgb(11, 0, 128); background-image: none;" title="University of California, San Diego">University of California, San Diego</a></li> <li style="margin-bottom: 0.1em;"><a rel="nofollow" class="external text" href="http://www.nature.com/polopoly_fs/7.9746!/file/Crick%20letter%20to%20Michael.pdf" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(http://upload.wikimedia.org/wikipedia/commons/2/23/Icons-mini-file_acrobat.gif); padding-right: 18px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Seven-page, handwritten letter that Crick sent to his 12-year-old son Michael in 1953 describing the structure of DNA.</a>&nbsp;See&nbsp;<a rel="nofollow" class="external text" href="http://www.nature.com/news/crick-s-medal-goes-under-the-hammer-1.12705" rel="nofollow" style="text-decoration: none; color: rgb(102, 51, 102); background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVR4Xn3PgQkAMQhDUXfqTu7kTtkpd5RA8AInfArtQ2iRXFWT2QedAfttj2FsPIOE1eCOlEuoWWjgzYaB/IkeGOrxXhqB+uA9Bfcm0lAZuh+YIeAD+cAqSz4kCMUAAAAASUVORK5CYII=); padding-right: 13px; background-position: 100% 50%; background-repeat: no-repeat no-repeat;">Crick&rsquo;s medal goes under the hammer</a>, Nature, 5 April 2013.</li>