BLASTbased

BLASTbased refers to analyses and workflows that rely on the Basic Local Alignment Search Tool (BLAST) and its variants to detect sequence similarity and infer biological information. In practice, BLASTbased methods use sequence comparisons to identify homologous regions, predict function, and classify organisms, often as part of genome annotation, transcript analysis, or metagenomics studies. The BLAST family includes BLASTN, BLASTP, BLASTX, tblastN and tblastx, each comparing nucleotide or amino acid sequences against nucleotide or protein databases. Key outputs include E-values, bit scores, percent identity and query coverage, which are interpreted to assess the significance of hits and potential functional or evolutionary relationships.

A typical BLASTbased workflow starts with selecting a query sequence and a suitable database, running the appropriate BLAST program, and then evaluating top hits for evidence of homology. Researchers consider alignment length, identity, and E-values, and may perform functional transfer from annotated hits, or manual curation to resolve ambiguous cases. Applications span gene annotation in newly sequenced genomes, prediction of protein function, identification of conserved domains, taxonomic binning in metagenomics, and construction of phylogenies based on homologous sequences.

Limitations include dependence on existing database content, reduced reliability for highly divergent or novel sequences, and the challenge of differentiating orthologs from paralogs. BLASTbased approaches are often supplemented by faster or more sensitive tools, such as DIAMOND or MMseqs2, especially for large-scale analyses.