Question

The positional difference for each word between the two sequences is obtained by ________ the position of the ______ sequence from that of the _______ sequence and is expressed as the offset.

(a) subtracting, second, first

(b) adding, second, first

(c) adding, first, second

(d) subtracting, first, second

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This key question is from FASTA topic in section Database Similarity Searching of Bioinformatics

Answer 1

Right option is (d) subtracting, first, second

Easiest explanation: The positional difference for each word between the two sequences is obtained by subtracting the position of the first sequence from that of the second sequence and is expressed as the offset. The ktups that have the same offset values are then linked to reveal a contiguous identical sequence region that corresponds to a stretch of diagonal in a two-dimensional matrix.