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== 2024.04.05 ==
=== DNA ===
'''Deoxyribonucleic acid''' ([https://en.wikipedia.org/wiki/Help:IPA/English /diːˈɒksɪˌraɪboʊnjuːˌkliːɪk, -ˌkleɪ-/] [https://en.wikipedia.org/wiki/File:En-us-Deoxyribonucleic_acid.ogg <sup>ⓘ</sup>];[https://en.wikipedia.org/wiki/DNA#cite_note-1 <sup>[1</sup>]] '''DNA''') is a [https://en.wikipedia.org/wiki/Polymer polymer] composed of two [https://en.wikipedia.org/wiki/Polynucleotide polynucleotide] chains that coil around each other to form a [https://en.wikipedia.org/wiki/Nucleic_acid_double_helix double helix]. The polymer carries [https://en.wikipedia.org/wiki/Genetics genetic] instructions for the development, functioning, growth and [https://en.wikipedia.org/wiki/Reproduction reproduction] of all known [https://en.wikipedia.org/wiki/Organism organisms] and many [https://en.wikipedia.org/wiki/Virus viruses]. DNA and [https://en.wikipedia.org/wiki/Ribonucleic_acid ribonucleic acid] (RNA) are [https://en.wikipedia.org/wiki/Nucleic_acid nucleic acids]. Alongside [https://en.wikipedia.org/wiki/Protein proteins], [https://en.wikipedia.org/wiki/Lipids lipids] and complex carbohydrates ([https://en.wikipedia.org/wiki/Polysaccharide polysaccharides]), nucleic acids are one of the four major types of [https://en.wikipedia.org/wiki/Macromolecule macromolecules] that are essential for all known forms of [https://en.wikipedia.org/wiki/Life life]. The two DNA strands are known as polynucleotides as they are composed of simpler [https://en.wikipedia.org/wiki/Monomer monomeric] units called [https://en.wikipedia.org/wiki/Nucleotide nucleotides].[https://en.wikipedia.org/wiki/DNA#cite_note-2 <sup>[2</sup>]][https://en.wikipedia.org/wiki/DNA#cite_note-3 <sup>[3</sup>]] Each nucleotide is composed of one of four [https://en.wikipedia.org/wiki/Nitrogenous_base nitrogen-containing] [https://en.wikipedia.org/wiki/Nucleobase nucleobases] ([https://en.wikipedia.org/wiki/Cytosine cytosine] [C], [https://en.wikipedia.org/wiki/Guanine guanine] [G], [https://en.wikipedia.org/wiki/Adenine adenine] [A] or [https://en.wikipedia.org/wiki/Thymine thymine] [T]), a [https://en.wikipedia.org/wiki/Monosaccharide sugar] called [https://en.wikipedia.org/wiki/Deoxyribose deoxyribose], and a [https://en.wikipedia.org/wiki/Organophosphate phosphate group]. The nucleotides are joined to one another in a chain by [https://en.wikipedia.org/wiki/Covalent_bond covalent bonds] (known as the [https://en.wikipedia.org/wiki/Phosphodiester_bond phosphodiester linkage]) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating [https://en.wikipedia.org/wiki/Backbone_chain sugar-phosphate backbone]. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to [https://en.wikipedia.org/wiki/Base_pair base pairing] rules (A with T and C with G), with [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen bonds] to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, the single-ringed [https://en.wikipedia.org/wiki/Pyrimidine pyrimidines] and the double-ringed [https://en.wikipedia.org/wiki/Purine purines]. In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. Both strands of double-stranded DNA store the same [https://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology#Biological_sequence_information biological information]. This information is [https://en.wikipedia.org/wiki/DNA_replication replicated] when the two strands separate. A large part of DNA (more than 98% for humans) is [https://en.wikipedia.org/wiki/Non-coding_DNA non-coding], meaning that these sections do not serve as patterns for [https://en.wikipedia.org/wiki/Primary_protein_structure protein sequences]. The two strands of DNA run in opposite directions to each other and are thus [https://en.wikipedia.org/wiki/Antiparallel_(biochemistry) antiparallel]. Attached to each sugar is one of four types of nucleobases (or ''bases''). It is the [https://en.wikipedia.org/wiki/Nucleic_acid_sequence sequence] of these four nucleobases along the backbone that encodes genetic information. [https://en.wikipedia.org/wiki/RNA RNA] strands are created using DNA strands as a template in a process called [https://en.wikipedia.org/wiki/Transcription_(genetics) transcription], where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes [https://en.wikipedia.org/wiki/Uracil uracil] (U).[https://en.wikipedia.org/wiki/DNA#cite_note-4 <sup>[4</sup>]] Under the [https://en.wikipedia.org/wiki/Genetic_code genetic code], these RNA strands specify the sequence of [https://en.wikipedia.org/wiki/Amino_acid amino acids] within proteins in a process called [https://en.wikipedia.org/wiki/Translation_(genetics) translation]. Within eukaryotic cells, DNA is organized into long structures called [https://en.wikipedia.org/wiki/Chromosome chromosomes]. Before typical [https://en.wikipedia.org/wiki/Cell_division cell division], these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. [https://en.wikipedia.org/wiki/Eukaryote Eukaryotic organisms] ([https://en.wikipedia.org/wiki/Animal animals], [https://en.wikipedia.org/wiki/Plant plants], [https://en.wikipedia.org/wiki/Fungus fungi] and [https://en.wikipedia.org/wiki/Protist protists]) store most of their DNA inside the [https://en.wikipedia.org/wiki/Cell_nucleus cell nucleus] as [https://en.wikipedia.org/wiki/Nuclear_DNA nuclear DNA], and some in the [https://en.wikipedia.org/wiki/Mitochondrion mitochondria] as [https://en.wikipedia.org/wiki/Mitochondrial_DNA mitochondrial DNA] or in [https://en.wikipedia.org/wiki/Chloroplast chloroplasts] as [https://en.wikipedia.org/wiki/Chloroplast_DNA chloroplast DNA].[https://en.wikipedia.org/wiki/DNA#cite_note-5 <sup>[5</sup>]] In contrast, [https://en.wikipedia.org/wiki/Prokaryote prokaryotes] ([https://en.wikipedia.org/wiki/Bacteria bacteria] and [https://en.wikipedia.org/wiki/Archaea archaea]) store their DNA only in the [https://en.wikipedia.org/wiki/Cytoplasm cytoplasm], in [https://en.wikipedia.org/wiki/Circular_chromosome circular chromosomes]. Within eukaryotic chromosomes, [https://en.wikipedia.org/wiki/Chromatin chromatin] proteins, such as [https://en.wikipedia.org/wiki/Histone histones], compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.<br/> <br/> full text link : [https://en.wikipedia.org/wiki/DNA https://en.wikipedia.org/wiki/DNA]
=== RNA ===
