Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Which of the following are geometric series?
P. 1, 6, 11, 16, 21, 26, ...
Options:
(A) Option A
(B) Option B
(C) Option C
(D) Option D
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.23)**
**1. Governing Concept**:
- **Topic**: Molecular Evolution & Horizontal Gene Transfer in Bacteria
- Bacterial genetic diversity in nature is driven by Horizontal Gene Transfer (HGT):
- **P. Conjugation**: Direct cell-cell contact and plasmid/conjugative transposon transfer via sex pilus $\rightarrow$ **INCREASES DIVERSITY**.
- **Q. Transformation**: Active uptake and chromosomal integration of exogenous free naked DNA from the environment $\rightarrow$ **INCREASES DIVERSITY**.
- **R. Transduction**: Bacteriophage-mediated transfer of bacterial host DNA between cells $\rightarrow$ **INCREASES DIVERSITY**.
- **S. Transfection**: Laboratory-induced uptake of viral or plasmid DNA into eukaryotic cells (or protoplasts); not a primary natural prokaryotic mechanism.
- In nature, the three classical natural parasexual mechanisms increasing bacterial diversity are **Conjugation, Transformation, and Transduction (P, Q, and R only)**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Incomplete set.
- **Option (B) is INCORRECT**: Excludes transduction.
- **Option (C) [P, Q and R only] is CORRECT**: The three canonical natural horizontal gene transfer mechanisms in bacteria.
- **Option (D) is INCORRECT**: Transfection is primarily an artificial laboratory technique.
**3. Final Answer**:
- **Correct Choice**: **B**
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