Overview
The BLAST (Basic Local Alignment Search Tool) algorithm is a bioinformatics method for rapidly comparing a biological query sequence against a database to find regions of local similarity between nucleotide or protein sequences. It works heuristically by first identifying short high-scoring matches (seeds or words) and then extending them into longer local alignments, scoring each with substitution matrices and reporting statistical measures such as the expect (E) value that estimate how likely a match is to arise by chance. BLAST matters because exact alignment of every possible sequence pair is computationally expensive, and its speed makes large-scale sequence searching practical for everyday research. Key applications include identifying unknown genes or proteins, inferring evolutionary relationships through homology, annotating newly sequenced genomes, detecting conserved motifs and domains, and supporting comparative genomics, proteomics, and drug-discovery workflows. Several BLAST variants exist, including nucleotide-versus-nucleotide, protein-versus-protein, and translated searches that bridge the two. Related peer-reviewed open-access research on bioinformatics tools and their role in biotechnology is available, illustrating how alignment methods like BLAST integrate with broader sequence-management, homology-modelling, and annotation pipelines.