The Blast Percent Identity Calculator is a vital tool in bioinformatics, commonly used in the analysis of DNA, RNA, or protein sequences to assess the similarity between two sequences aligned by a BLAST search. This calculator provides critical insights into evolutionary relationships, gene identity, and function prediction by quantifying the exact match between sequences.
Formula of Blast Percent Identity Calculator
Percent Identity = (Number of Identical Matches / Alignment Length) * 100
Where:
- Number of Identical Matches: The number of positions in the alignment where the sequences have exactly the same nucleotide or amino acid.
- Alignment Length: The total number of positions in the alignment, which includes matches, mismatches, and any gaps that occur during alignment.
General Reference Table
To provide a quick reference for typical scenarios where this calculator is used, the following table lists different types of sequence comparisons and their expected percent identity ranges:
| Comparison Type | Typical Percent Identity Range |
|---|---|
| Highly conserved genes | 80-100% |
| Homologous genes in different species | 40-80% |
| Random sequences | Below 10% |
This table helps users to quickly estimate and interpret the percent identity in various biological and evolutionary contexts.
Example of Blast Percent Identity Calculator
Consider a researcher comparing two DNA sequences from different species to determine how closely related they are. If the alignment results show 450 identical matches out of an alignment length of 600 bases, the percent identity would be calculated as follows:
- Number of Identical Matches = 450
- Alignment Length = 600
Calculation:
- Percent Identity = (450 / 600) * 100 = 75%
This result suggests a strong evolutionary relationship between the two species, reflecting a high degree of similarity in the compared DNA regions.
Most Common FAQs
Gaps reduce the percent identity because they increase the alignment length without increasing the number of identical matches.
A low percent identity typically indicates that the sequences are not closely related, which could mean they have different functions or belong to different evolutionary lineages.
While percent identity can provide clues about similarity, protein function predictions often require more detailed analyses including conserved domains, structure, and active sites.