Which type of BLAST can be used to compare an amino acid query sequence against a protein sequence database? BLASTN BLASTX tBLASTn BLASTP

To determine which type of BLAST can be used to compare an amino acid query sequence against a protein sequence database, let's analyze each option:

1. BLASTN: This is used to compare a nucleotide sequence against a nucleotide sequence database. Therefore, it cannot be used for amino acid queries.

2. BLASTX: This tool translates a nucleotide query sequence in all six reading frames and compares the resulting peptide sequences against a protein sequence database. However, it starts with nucleotide sequences, not amino acid sequences.

3. tBLASTn: This is used to compare a protein query sequence against a nucleotide database that is translated in all six reading frames. While it allows for comparisons against translated sequences, it does not directly apply to comparing an amino acid query against a protein database.

4. BLASTP: This is designed specifically for comparing a protein query sequence against a protein sequence database. It allows for direct comparison of amino acid sequences, making it the correct choice.

Final Answer

BLASTP is the type of BLAST that can be used to compare an amino acid query sequence against a protein sequence database.