Multiple Sequence Alignment Score Calculator

The Multiple Sequence Alignment Score Calculator quantifies how well a group of biological sequences — protein, DNA, or RNA — align with one another, a key step in evolutionary and structural analysis. Paste your pre-aligned sequences in FASTA format, then select a scoring matrix (BLOSUM62, PAM250, or Identity), set your gap opening and gap extension penalties, and choose your sequence type to get the Total Alignment Score. Secondary outputs include Average Pairwise Score, Overall Identity %, and Gap Percentage.

Paste aligned sequences in FASTA format

Sequence Type *

Adjust score based on alignment length

Results

Total Alignment Score

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Average Pairwise Score

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Overall Identity

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Gap Percentage

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Results Table

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Frequently Asked Questions

What is a multiple sequence alignment score?

A multiple sequence alignment score quantifies the quality of an alignment by considering matches, mismatches, and gaps between sequences. Higher scores indicate better alignments with more conserved regions.

How do gap penalties affect alignment scoring?

Gap opening penalties are applied when a gap is introduced, while gap extension penalties are applied for each position the gap continues. Higher penalties discourage gaps and favor longer continuous matches.

Which scoring matrix should I use for my sequences?

BLOSUM62 is recommended for protein sequences with moderate evolutionary distance. PAM250 works better for distantly related proteins. Use identity matrix for exact match scoring.

What does the identity percentage represent?

Identity percentage shows the proportion of positions where all sequences have identical residues. It's a measure of sequence conservation across the entire alignment.

Should I normalize scores by alignment length?

Yes, normalizing by length makes scores comparable between alignments of different sizes and accounts for the tendency of longer alignments to have higher raw scores.

How is the average pairwise score calculated?

The average pairwise score is computed by scoring all possible sequence pairs in the alignment and taking their mean. This provides insight into overall alignment quality.

What input format is required for sequences?

Sequences should be provided in FASTA format with sequence names preceded by '>' and aligned sequences on separate lines. Gaps should be represented with '-' characters.