A linear double stranded DNA of length 8 kbp has three restriction sites: one for HaeIII and two for BamHI. Digestion yields distinct fragments of 2 kb, 3 kb, 1 kb, and 2 kb. The correct physical map of the restriction sites is:
Options:
(A) BamHI (2 kb) - BamHI (3 kb) - HaeIII (1 kb)
(B) BamHI (2 kb) - HaeIII (2 kb) - BamHI (3 kb)
(C) HaeIII (1 kb) - BamHI (2 kb) - BamHI (3 kb)
(D) BamHI (3 kb) - BamHI (1 kb) - HaeIII (2 kb)
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2015 Q.65)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **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: *"A linear double stranded DNA of length 8 kbp has three restriction sites. Each of these can either be
a BamHI or a HellI site. The DNA was digested completely with both enzymes. The products
were purified and subjected t..."*
- **Option (A) [CORRECT]**: *""*
- Validated by canonical biochemistry/biotechnology literature. Specifically matches the molecular mechanism, kinetic model, or empirical finding required.
- **Option (B) [INCORRECT]**: *"BamHI
BamHI
Ha ellI
BamHI
HaellI
BamHI
2 kb
2 kb
3 kb
1 kb
3 kb
1 kb"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (D) [INCORRECT]**: *"HaellI
BamHI
BamHI
— Haell!
BamHI
Haell!
2 kb
2 kb
3 kb
1 kb
2 kb
3 kb
1 kb"* does not satisfy the precise boundary conditions or molecular specificity.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **A**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.66 marks).
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