Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Which of the following characteristics with respect to bacterial DNA polymerases is/are TRUE?
P. DNA Polymerase I has 5' to 3' exonuclease proofreading activity
Q. DNA Polymerase III is the primary replicative polymerase
R. DNA Polymerase I requires RNA primers for in vivo initiation
S. DNA Polymerase II has reverse transcriptase activity
Options:
(A) P and S only
(B) P, Q and R only
(C) Q and S only
(D) R and S only
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2011 Q.43)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: Biotechnology
- **Question Type**: **MCQ** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Systematic Conceptual & Option-by-Option Evaluation**:
- Problem Focus: *"Which of the following characteristics with respect to bacterial DNA polymerases is/are TRUE?
P. DNA Polymerase I has 5' to 3' exonuclease proofreading activity
Q. DNA Polymerase III is the primary replicative polymerase..."*
- **Option (B) [CORRECT]**: *"P, Q and R only"*
- Validated by canonical biochemistry/biotechnology literature. Specifically matches the molecular mechanism, kinetic model, or empirical finding required.
- **Option (A) [INCORRECT]**: *"P and S only"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (C) [INCORRECT]**: *"Q and S only"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (D) [INCORRECT]**: *"R and S only"* does not satisfy the precise boundary conditions or molecular specificity.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.66 marks).
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