Sequence Alignment Score Calculator

Global alignment (Needleman-Wunsch) aligns sequences end-to-end, considering the entire length of both sequences. Local alignment (Smith-Waterman) finds the best matching subsequences within the sequences, ignoring poorly matching regions.

Gap opening penalty is applied when starting a new gap, while gap extension penalty is applied for each position the gap continues. Higher penalties discourage gaps, leading to more substitutions in the alignment.

Sequence identity is the percentage of positions where both sequences have exactly the same nucleotide or amino acid. It's calculated as (identical positions / alignment length) × 100.

Yes, you can align both DNA and protein sequences. Select the appropriate sequence type to ensure proper scoring. DNA sequences use A, T, G, C nucleotides while protein sequences use the 20 standard amino acids.

Alignment scores depend on sequence length and scoring parameters. Higher positive scores indicate better alignments. Compare scores relative to random sequence alignments or use normalized scores like bit scores for meaningful interpretation.

Identity counts only exact matches, while similarity includes biochemically similar substitutions. For proteins, this includes amino acids with similar properties (e.g., hydrophobic or charged residues).

This tool uses a simple match/mismatch scoring system. For more sophisticated protein alignment, consider tools that implement BLOSUM or PAM matrices which account for amino acid substitution frequencies.

Negative scores occur when sequences are poorly related and the penalties for mismatches and gaps outweigh the rewards for matches. This suggests the sequences may not be homologous or may require different alignment parameters.