GATE BT 2019 • Q41
MCQ • 2 Marks
Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Which of the following factors affect the fidelity of DNA polymerase in polymerase chain
reaction?
P. Mg concentration
Q. pH
R. Annealing temperature
Options:
-
(A) P and Q only
-
(B) P and R only
-
(C) Q and R only
-
(D) P, Q and R
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.41)**
**1. Governing Concept**:
- **Topic**: Molecular Biology & PCR Fidelity
- The fidelity of DNA synthesis during Polymerase Chain Reaction (accuracy of copying without introducing mutations) is governed by:
1. **Proofreading activity**: Presence of $3' \rightarrow 5'$ exonuclease proofreading activity in the DNA polymerase (e.g., *Pfu* or *Q5* vs. non-proofreading *Taq*).
2. **Divalent cation concentration**: Excess free $\text{Mg}^{2+}$ concentration lowers fidelity by stabilizing non-Watson-Crick mispaired bases.
3. **dNTP pool concentrations and balance**: Imbalanced or excessively high dNTP concentrations increase misincorporation rates.
**2. Option Analysis**:
- **Option (A) is CORRECT**: Formally includes proofreading exonuclease activity, magnesium concentration, and balanced dNTP pools.
- **Option (B) is INCORRECT**: Incomplete factor list.
- **Option (C) is INCORRECT**: Disregards proofreading enzyme specificity.
- **Option (D) is INCORRECT**: Denaturation temperature alone does not dictate fidelity.
**3. Final Answer**:
- **Correct Choice**: **A**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.
Launch CBT Mock Test