Question

Sequence similarity and sequence identity are synonymous for nucleotide sequences and protein sequences as well.

(a) True

(b) False

I have been asked this question in an online quiz.

My query is from Sequence Homology Versus Sequence Similarity and Identity topic in division Pairwise Sequence Alignment of Bioinformatics

Answer 1

Correct answer is (b) False

Easiest explanation: Sequence similarity and sequence identity are synonymous for nucleotide sequences. For protein sequences, however, the two concepts are very different. In a protein sequence alignment, sequence identity refers to the percentage of matches of the same amino acid residues between two aligned sequences. Similarity refers to the percentage of aligned residues that have similar physicochemical characteristics and can be more readily substituted for each other.