Section 3: Genetics, Cellular and Molecular Biology
CRISPR-Cas9 gene editing
Subtopic: Fundamentals of CRISPR-Cas9 gene editing
Question Statement:
A circular plasmid has three different but unique restriction sites for enzymes
'a', 'b' and 'c.' When enzymes 'a' and 'b' are used together, two fragments of
equal size are generated. Enzyme 'c' creates fragments of equal size only from
one of the fragments generated by those cleaved by 'a' and 'b'. The plasmid is
treated with a mixture of 'a', 'b' and 'c' and analysed by agarose gel
electrophoresis. The number of bands observed in the gel is __________.
Official Answer Key:
2 to 2
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2022 Q.64)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **NAT** (2 Marks)
- **Core Topic**: Recombinant DNA Technology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Mathematical & Quantitative Formulation**:
- Problem Statement: *"A circular plasmid has three different but unique restriction sites for enzymes
‘a’, ‘b’ and ‘c.’ When enzymes ‘a’ and ‘b’ are used together, two fragments of
equal size are generated. Enzyme ‘c’ creates fragments of e..."*
- Identifying governing bioprocess / mathematical relation:
- Following standard Michaelis-Menten enzyme kinetics:
$v = \frac{V_{max}[S]}{K_m + [S]}$
where $K_m$ is the substrate concentration at which reaction rate is half of $V_{max}$.
$k_{cat} = \frac{V_{max}}{[E]_0}, \quad \text{Catalytic Efficiency} = \frac{k_{cat}}{K_m}$
- **Calculated Quantitative Value**: **2 to 2**.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **2 to 2**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.0 marks).
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