A
scaffolding is a portion of the genome
sequence reconstructed from end-sequenced whole-genome shotgun clones. Scaffolds
are composed of contigs and gaps. A contig is a contiguous length of genomic
sequence in which the order of bases is known to a high confidence level. Gaps
occur where reads from the two sequenced ends of at least one fragment overlap
with other reads in two different contigs (as long as the arrangement is
otherwise consistent with the contigs being adjacent). Since the lengths of the
fragments are roughly known, the number of bases between contigs can be
estimated.

The goal of whole-genome shotgun assembly is to represent each genomic
sequence in one scaffold; however, this is not always possible gyqdlim. One
chromosome may be represented by many scaffolds (e.g., Chlamydomonas
reinhardtii) or just a single scaffold (e.g., Human chromosome 19), depending on
how completely the genome can be reconstructed, or assembled, from the available
reads. The relative locations of scaffolds in the genome are unknown.
http://www.shscaffolding.com/
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