Section 3: Genetics, Cellular and Molecular Biology
DNA replication, transcription, translation
Subtopic: Fundamentals of DNA replication, transcription, translation
Question Statement:
Which one of the following tools is used to compare all the possible six-open
reading frames of a given nucleotide query sequence with all the available
six-open reading frames of the nucleotide sequence database?
Options:
(A) | BLASTN
(B) BLASTX
(C) TBLASTN
(D) TBLASTX
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.42)**
**1. Governing Concept**:
- **Topic**: Bioinformatics & BLAST Sequence Alignment Variants
- Comparison of all 6 reading frames:
- **BLASTN**: Nucleotide query vs. Nucleotide database (no translation).
- **BLASTP**: Protein query vs. Protein database.
- **BLASTX**: Nucleotide query translated in 6 frames vs. Protein database.
- **TBLASTN**: Protein query vs. 6-frame translated Nucleotide database.
- **TBLASTX**: Translates **both** the nucleotide query sequence in all 6 reading frames AND the nucleotide database sequences in all 6 reading frames, performing pairwise protein comparison across all 36 reading frame combinations.
**2. Option Analysis**:
- **Option (A) [BLASTN] is INCORRECT**: Direct nucleotide alignment without translation.
- **Option (B) [BLASTX] is INCORRECT**: Translates query only, searches protein database.
- **Option (C) [TBLASTN] is INCORRECT**: Protein query searched against translated nucleotide database.
- **Option (D) [TBLASTX] is CORRECT**: Specifically compares 6-frame translated query against 6-frame translated database.
**3. Final Answer**:
- **Correct Choice**: **D**
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