Variants of BLAST

• BLASTN - Compares a DNA query to a DNA database. Searches both strands automatically. It is optimized for speed, rather than sensitivity.
• BLASTP - Compares a protein query to a protein database.
• BLASTX - Compares a DNA query to a protein database, by translating the query sequence in the 6 possible frames, and comparing each against the database (3 reading frames from each strand of the DNA) searching.
• TBLASTN - Compares a protein query to a DNA database, in the 6 possible frames of the database.
• TBLASTX - Compares the protein encoded in a DNA query to the protein encoded in a DNA database, in the 6*6 possible frames of both query and database sequences (Note that all the combinations of frames may have different scores).
• BLAST2 - Also called advanced BLAST. It can perform gapped alignments.
• PSI-BLAST - (Position Specific Iterated) Performs iterative database searches (details below).