Difference between revisions of "DNA Sequencing"

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imported>Eunjin RYU
imported>Eunjin RYU
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<p><span style="font-size:14px">In genetics&nbsp;and biochemistry, sequencing&nbsp;means to determine the primary structure&nbsp;of an unbranched biopolymer.&nbsp;Sequencing results in a symbolic linear depiction known as a sequence&nbsp;which succinctly summarizes much of the atomic-level structure of the sequenced molecule.</span></p>
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<p><span style="font-size:14px">Sequencing is the method&nbsp;to determine&nbsp;biopolymer&#39;s primary sequence.&nbsp;Sequencing results in a linear string of symbolic letters&nbsp;which&nbsp;summarize important information of genome by genetic code - A, T, G, C.</span></p>
  
 
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<p><span style="font-size:14px">The whole genome can&#39;t be sequenced all at once because available methods of DNA sequencing can only handle short stretches of DNA at a time. So instead, scientists must break the genome into small pieces, sequence the pieces, and then reassemble them in the proper order. An automatic sequencing machine spits out what genome scientists call &quot;raw&quot; sequence. In raw sequence, the reads or short DNA sequences are all jumbled together. The process of transforming the fragmented rough draft into a long, continuous final product without breaks or errors is called finishing. Finishing often takes longer than the sequencing itself.</span></p>
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<p><span style="font-size:14px">It&#39;s almost impossible to sequence whole genome at once since existing DNA sequencing methods are limited in handling short-stratches at a time. As a result, researchers break down the genome into small fragments and reasseble these fragments into order of&nbsp;original long string. The process of transition&nbsp;of fragmented reads into a long and continuous sequence is assembly. Assembly or alignment takes more time than the sequencing.</span></p>
  
 
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<p><span style="font-size:14px">To facilitate their full genome sequencing initiatives, &ldquo;Illumina&rdquo; licensed nanopore sequencing technology from Oxford Nanopore Technologies. Illumina sequencing system based on reversible terminators for sequence determination. It is an approach that generates several billion bases of accurate nucleotide sequence per experiment at low cost. Single molecules of DNA are attached to a flat surface, amplified in situ and used as templates for synthetic sequencing with fluorescent reversible terminator deoxyribonucleotides. Another possible way to accomplish cost-effective high-throughput sequencing is by utilizing fluorophore technology. Pacific Biosciences is currently using this approach in their SMRT (Single Molecule Real Time) DNA sequencing technology. SMRT sequencing is a harnesses the natural process of DNA replication and enables real-time observation of DNA synthesis by using phosphorlinked nucleotides.</span></p>
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<p><span style="font-size:14px">&ldquo;Illumina&rdquo; licensed&nbsp;sequencing technology using nanopores&nbsp;from Oxford Nanopore Technologies. For sequencing determination,&nbsp;Illumina sequencing system use&nbsp;reversible terminators.&nbsp;Single molecules of DNA are attached to a flat support material, amplified in situ and used as templates for synthetic sequencing with fluorescent reversible terminator deoxyribonucleotides. Another possible way to&nbsp;sequence&nbsp;is by using fluorophore technology. &quot;Pacific Biosciences&quot; is currently SMRT (Single Molecule Real Time) DNA sequencing technology. SMRT sequencing is a harnesses the natural process of DNA replication and can&nbsp;real-time observation of DNA replication by using phosphorlinked deoxyribonucleotides.</span></p>
  
 
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Revision as of 00:08, 11 December 2015

DNA Sequencing

 

 

 

What is Sequencing?

 

Sequencing is the method to determine biopolymer's primary sequence. Sequencing results in a linear string of symbolic letters which summarize important information of genome by genetic code - A, T, G, C.

 

Why sequencing is important?

 

Genome sequencing is figuring out the order of DNA nucleotides, or bases. When you read a sentence, the meaning is not just in the sequence of the letters. It is also in the words those letters make and in the grammar of the language. Similarly, the human genome is more than just its sequence. Sequencing the genome is an important step towards understanding it. Scientists also hope that being able to study the entire genome sequence will help them understand how the genome works—how genes work together to direct the growth, development and maintenance of an entire organism. Finally, genes account for less than 25 percent of the DNA in the genome, and so knowing the entire genome sequence will help scientists study the parts of the genome outside the genes. This includes the regulatory regions that control how genes are turned on an off, as well as long stretches of junk DNA.

 

How sequencing is operated?

 

It's almost impossible to sequence whole genome at once since existing DNA sequencing methods are limited in handling short-stratches at a time. As a result, researchers break down the genome into small fragments and reasseble these fragments into order of original long string. The process of transition of fragmented reads into a long and continuous sequence is assembly. Assembly or alignment takes more time than the sequencing.

 

Which kinds of sequencing techniques are available?

 

“Illumina” licensed sequencing technology using nanopores from Oxford Nanopore Technologies. For sequencing determination, Illumina sequencing system use reversible terminators. Single molecules of DNA are attached to a flat support material, amplified in situ and used as templates for synthetic sequencing with fluorescent reversible terminator deoxyribonucleotides. Another possible way to sequence is by using fluorophore technology. "Pacific Biosciences" is currently SMRT (Single Molecule Real Time) DNA sequencing technology. SMRT sequencing is a harnesses the natural process of DNA replication and can real-time observation of DNA replication by using phosphorlinked deoxyribonucleotides.

 

References

 

  1. https://en.wikipedia.org/wiki/Sequencing
  2. http://www.genomenewsnetwork.org/resources/whats_a_genome/Chp2_1.shtml
  3. N/A. (2008). Accurate Whole Human Genome Sequencing using Reversible Terminator Chemistry. Nature. 456(7218): 53–59.
  4. Xiaoge, G., Kevin, L., Karen, O., Jenny Z., Sandeep S. D., & Sue J.R. (2015). SMRT Sequencing for Parallel Analysis of Multiple Targets and Accurate SNP Phasing. G3. g3.115.023317