Editing Sequence assembly (section)

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In [[bioinformatics]], '''sequence assembly''' refers to [[sequence alignment|aligning]] and merging fragments from a longer [[DNA]] sequence in order to reconstruct the original sequence.<ref name="Sohn_2018">{{cite journal | vauthors = Sohn JI, Nam JW | title = The present and future of de novo whole-genome assembly | journal = Briefings in Bioinformatics | volume = 19 | issue = 1 | pages = 23–40 | date = January 2018 | pmid = 27742661 | doi = 10.1093/bib/bbw096 }}</ref> This is needed as [[DNA sequencing]] technology might not be able to 'read' whole genomes in one go, but rather reads small pieces of between 20 and 30,000 bases, depending on the technology used.<ref name="Sohn_2018" /> Typically, the short fragments (reads) result from [[shotgun sequencing]] [[genome|genomic]] DNA, or [[Transcription (genetics)|gene transcript]] ([[expressed sequence tag|ESTs]]).<ref name="Sohn_2018" />

The problem of sequence assembly can be compared to taking many copies of a book, passing each of them through a shredder with a different cutter, and piecing the text of the book back together just by looking at the shredded pieces. Besides the obvious difficulty of this task, there are some extra practical issues: the original may have many repeated paragraphs, and some shreds may be modified during shredding to have typos. Excerpts from another book may also be added in, and some shreds may be completely unrecognizable.