Section 3: Genetics, Cellular and Molecular Biology
DNA replication, transcription, translation
Subtopic: Fundamentals of DNA replication, transcription, translation
Question Statement:
BLAST and its extensions can be used to determine similarity of a query protein
sequence with which of the following database(s)?
Options:
(A) A database of translated nucleotide sequences
(B) A database of binding ligands and small translated peptides
(C) A database of protein structures
(D) A database of binding, linking and self-assembling proteins
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.30)**
**1. Governing Concept**:
- **Topic**: Bioinformatics & Sequence Similarity Searching (BLAST Algorithms)
- **BLAST (Basic Local Alignment Search Tool)** family tools:
- **BLASTP**: Compares an amino acid query sequence against a protein sequence database.
- **BLASTX**: Compares a nucleotide query sequence translated in all six reading frames against a protein sequence database.
- **TBLASTN**: Compares a protein query sequence against a nucleotide sequence database dynamically translated in all six frames.
- **TBLASTX**: Compares a six-frame translated nucleotide query against a six-frame translated nucleotide database.
**2. Option Analysis**:
- **Option (A) [a protein query against a translated nucleotide database (tblastn)] is CORRECT**: TBLASTN specifically takes a protein query and searches it against a 6-frame translated nucleotide database.
- **Option (B) [blastx] is INCORRECT**: BLASTX takes a nucleotide query (translating it in six frames) and queries a protein database (not a protein query).
- **Option (C) [a translated nucleotide query against a protein database (tblastn)] is INCORRECT**: That describes BLASTX, not TBLASTN.
- **Option (D) is INCORRECT**: Inverted database/query translation designations.
**3. Final Answer**:
- **Correct Option**: **A**
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