DNA Sequencing
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
- https://en.wikipedia.org/wiki/Sequencing
- http://www.genomenewsnetwork.org/resources/whats_a_genome/Chp2_1.shtml
- N/A. (2008). Accurate Whole Human Genome Sequencing using Reversible Terminator Chemistry. Nature. 456(7218): 53–59.
- 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
