Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Shown below is a plasmid vector (P) and an insert (Q). The insert was cloned into the BamHI site
of the vector. The recombinant plasmid was isolated and digested with BamHI or Xhol. The results
from the digestion experiments are shown in (R).
BamHi
DNA ladder
BamHI
thai
6 kb
5 kb
5 kb plasmid
vector
BamHI
Xhol
BamHI|
4 kb
Q.3 kb 1
3 kb
1 kb insert
2 kb
1 kb
ECORI
Q
R
Which one of the following explains the digestion results shown in (R)?
Options:
(A) The insert did not ligate to the vector.
(B) One copy of the insert ligated to the vector.
(C) The insert ligated to the vector as two tandem copies.
(D) The insert ligated to the vector as two copies but not in tandem.
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2017 Q.43)**
**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: *"Shown below is a plasmid vector (P) and an insert (Q). The insert was cloned into the BamHI site
of the vector. The recombinant plasmid was isolated and digested with BamHI or Xhol. The results
from the digestion experim..."*
- 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 $pprox 110 ext{ Da}$.
$\text{Number of base pairs} = \frac{\text{Molecular Weight (Da)}}{660\text{ Da/bp}}$
- **Official Answer Key Interval**: Evaluated numerical range is **3.5 to 3.7** (Target value: **3.5 to 3.7**).
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **3.5 to 3.7**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.0 marks).
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