Difference Between Similarity and Identity in Sequence Alignment | Similarity vs Identity in Sequence Alignment

The key difference between similarity and identity in sequence alignment is that similarity is the likeness (resemblance) between two sequences in comparison while identity is the number of characters that match exactly between two different sequences.

Bioinformatics is an interdisciplinary field of science that mainly involves molecular biology and genetics, computer science, mathematics, and statistics. Sequence alignment is a major term in bioinformatics. It is the procedure in which the sequences of DNA, RNA or protein are arranged to identify regions of resemblance that is a consequence of functional, structural or evolutionary relationship between the sequences. At the end of the alignment, they will be presented as rows within a matrix. In order to align the identical characters in successive coloums, inserted gaps are present between the residues.


1. Overview and Key Difference
2. What is Similarity in Sequence Alignment
3. What is Identity in Sequence Alignment
4. Similarities Between Similarity and Identity in Sequence Alignment
5. Side by Side Comparison – Similarity vs Identity in Sequence Alignment in Tabular Form
6. Summary

What is Similarity?

Similarity in sequence alignment is the resemblance between two sequences when compared. This fact is dependent on the identity of sequences. Similarity depicts the extent to which the residues are aligned. Hence, similar sequences contain similar properties. In bioinformatics, similarity is a tool to assess the likeness between two proteins.