Difference Between Homology and Similarity in Bioinformatics | Homology vs Similarity in Bioinformatics

The key difference between homology and similarity in bioinformatics is that homology refers to a statement about common evolutionary ancestry of two sequences whilst similarity refers to the degree of likeness between two sequences.

Bioinformatics is a field of science that combines biology, information engineering, computer science, mathematics and statistics to analyze and interpret biological data. Homology and similarity are two terms we use in the field of bioinformatics. We can easily calculate the similarity as a percentage of similar residues over a given length of the alignment. However, we cannot calculate homology since it could be true or false and usually depend on the hypothesis used.


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

What is Homology in Bioinformatics?

Homology in bioinformatics refers to the biological homology between DNA, RNA and protein sequences which are defined in terms of shared ancestral properties in the evolutionary tree of life. In other words, it is the common evolutionary ancestry of two sequences. The reason for such occurrence could be either due to speciation events (orthologs), horizontal gene transfer events (xenologs) or duplication events (paralogs).