Question

Which one of the following programs is used for finding distantly related (or remote) protein homologs?

• A. BLASTN
• B. BLASTX
• C. PSI-BLAST
• D. TBLASTX

Hint:

- BLASTN: DNA vs DNA
- BLASTX: DNA translated vs protein
- TBLASTX: translated DNA vs translated DNA
- PSI-BLAST: best for distantly related proteins.

Answer 1

The Correct Option is C

Step 1: BLAST (Basic Local Alignment Search Tool) is used to compare biological sequences.
Step 2: PSI-BLAST (Position-Specific Iterated BLAST) improves sensitivity by building a position-specific scoring matrix (PSSM) from multiple sequence alignments.
Step 3: This allows PSI-BLAST to detect distantly related protein homologs that might not be found by a standard BLAST search.
Final Answer: PSI-BLAST is the program used to find remote protein homologs.
\[\boxed{\text{Correct Answer: (C)}}\]