Editing Shotgun sequencing (section)

{{Short description|Method used for sequencing random DNA strands}}
In [[genetics]], '''shotgun sequencing''' is a method used for [[sequencing]] random [[DNA]] strands. It is named by analogy with the rapidly expanding, quasi-random [[shot grouping]] of a [[shotgun]].
[[File:Simplified scheme of shotgun sequencing technique.png|thumb|Simplified scheme of shotgun sequencing technique: firstly, the DNA fragment is cut into small, overlapping pieces. Then each fragment is sequenced, and the complete sequence is assembled based on the similarity of the overlapping ends. This approach can be applied only to small genomes or fragments of bigger genomes due to the presence of multiple repeated sequences. 
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The [[Sanger sequencing#Method|chain-termination method]] of [[DNA sequencing]] ("Sanger sequencing") can only be used for short DNA strands of 100 to 1000 [[base pair]]s. Due to this size limit, longer sequences are subdivided into smaller fragments that can be sequenced separately, and these sequences are [[sequence assembly|assembled]] to give the overall sequence.
In shotgun sequencing,<ref name="Staden">{{cite journal |last1=Staden |first1=R. |title=A strategy of DNA sequencing employing computer programs |journal=Nucleic Acids Research |date=1979 |volume=6 |issue=7 |pages=2601–2610 |doi=10.1093/nar/6.7.2601 |pmid=461197 |pmc=327874}}</ref><ref>{{cite journal |last1=Anderson |first1=Stephen |title=Shotgun DNA sequencing using cloned DNase I-generated fragments |journal=Nucleic Acids Research |date=1981 |volume=9 |issue=13 |pages=3015–3027 |doi=10.1093/nar/9.13.3015 |pmid=6269069 |pmc=327328}}</ref> DNA is broken up randomly into numerous small segments, which are sequenced using the chain termination method to obtain ''reads''. Multiple overlapping reads for the target DNA are obtained by performing several rounds of this fragmentation and sequencing. Computer programs then use the overlapping ends of different reads to assemble them into a continuous sequence.<ref name="Staden" />

Shotgun sequencing was one of the precursor technologies that was responsible for enabling [[whole genome sequencing]].