Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
The direction of shell coiling in the snail Limnaea peregra is a classic example of
(A) chromosomal inheritance (B) extra-chromosomal inheritance
(C) chromosomal translocation (D) homologous recombination
Options:
(A) chromosomal inheritance
(B) extra-chromosomal inheritance
(C) chromosomal translocation
(D) homologous recombination
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2012 Q.14)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Systematic Conceptual & Option-by-Option Evaluation**:
- Problem Focus: *"The direction of shell coiling in the snail Limnaea peregra is a classic example of..."*
- **Option (B) [CORRECT]**: *"extra-chromosomal inheritance"*
- Validated by canonical biochemistry/biotechnology literature. Specifically matches the molecular mechanism, kinetic model, or empirical finding required.
- **Option (A) [INCORRECT]**: *"chromosomal inheritance"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (C) [INCORRECT]**: *"chromosomal translocation"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (D) [INCORRECT]**: *"homologous recombination"* does not satisfy the precise boundary conditions or molecular specificity.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: 1 Mark (Negative marking: -0.33 marks).
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