Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Plasmid DNA (0.5 kg) containing an ampicillin resistance marker was added to 200 ul of
competent cells. The transformed competent cells were diluted 10,000 times, out of which, 50 pl
was plated on agar plates containing ampicillin. A total of 35 colomes were obtained. The
transformation efficiency is _
_× 10° cfu ug-1
2.8
Official Answer Key:
2.8 to 2.8
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2015 Q.46)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **NAT** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Mathematical & Quantitative Formulation**:
- Problem Statement: *"Plasmid DNA (0.5 kg) containing an ampicillin resistance marker was added to 200 ul of
competent cells. The transformed competent cells were diluted 10,000 times, out of which, 50 pl
was plated on agar plates containing ..."*
- Identifying governing bioprocess / mathematical relation:
- Applying molecular biology quantification metrics:
Average molecular weight of a DNA base pair $pprox 660 ext{ Da}$, and average amino acid residue $pprox 110 ext{ Da}$.
$\text{Number of base pairs} = \frac{\text{Molecular Weight (Da)}}{660\text{ Da/bp}}$
- **Calculated Quantitative Value**: **2.8 to 2.8**.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **2.8 to 2.8**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.0 marks).
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