Sequence comparison
Sequence similarity can suggest shared ancestry or function, but chance matches also occur.
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Sequence similarity can suggest shared ancestry or function, but chance matches also occur. An alignment proposes corresponding positions with substitutions and gaps; edit distance counts simple changes under a chosen cost model. A k-mer is a substring of length k and can summarize local sequence content. Interpret similarity in light of sequence length and an appropriate null comparison.
Worked example
ATGC and ATCC differ by one substitution, so their simple Hamming distance is one. For an insertion, an alignment or edit distance is more appropriate than position-wise comparison.