Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
The order of genes present in a chromosome is as follows.
L M
NOP Q
Which one of the following rearrangements represents a paracentric inversion?
Options:
(A) LO N
M P Q
(B) L M
NP 0 Q
(C) I M M
NNOPe
(D) LM N
0P Q
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.16)**
**1. Governing Concept**:
- **Topic**: Genetics & Chromosomal Inversions
- Given standard gene order: $L\ M\ \bullet\ N\ O\ P\ Q$ (where $\bullet$ represents the centromere).
- Types of inversions:
- **Paracentric inversion**: The inverted chromosomal segment does **NOT include the centromere** (confined to a single chromosome arm).
- **Pericentric inversion**: The inverted segment **includes the centromere**.
- In $L\ M\ \bullet\ N\ P\ O\ Q$, the segment $O-P$ on the right arm is inverted to $P-O$ without involving the centromere, representing a **paracentric inversion**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Segment $M \bullet N O$ inverted across the centromere (pericentric inversion).
- **Option (B) [L M · N P O Q] is CORRECT**: The inverted region ($N P O$) is entirely on one side of the centromere (paracentric).
- **Option (C) is INCORRECT**: Chromosomal duplication/deletion rearrangement.
- **Option (D) is INCORRECT**: Duplication artifact.
**3. Final Answer**:
- **Correct Choice**: **B**
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