Table 1. BLAST programs provided by the National Center for Biotechnology Information

Program	Query sequence	Database	Type of alignment^a
BLASTP	Protein	Protein	Gapped
BLASTN	Nucleic acid	Nucleic acid	Gapped
BLASTX	Translated nucleic acid^b	Protein	Each frame gapped
TBLASTN	Protein	Translated nucleic acid^b	Each frame gapped
TBLASTX^c	Translated nucleic acid^b	Translated nucleic acid^b	Ungapped
^aType of alignment available between query and database sequences in BLAST2. A gapped alignment is usually preferred, if available. BLASTX and TBLASTN generate gapped alignment for each reading frame found and may use sum statistics. TBLASTX provides only ungapped alignments and sum statistics. Ungapped alignments available as option for BLASTP and BLASTN.
^bNucleic acid sequence is translated in all six possible reading frames and then compared with the protein sequence.
^cTBLASTX is a heavy user of computer resources and therefore cannot be used with the nr nucleic acid database on the BLAST Web page.