Q.72 Which one of the following is NOT involved in horizontal gene transfer?
(A) Conjugation (B) Transformation
(C) Transduction (D) Mutation
Horizontal gene transfer (HGT) involves DNA movement between organisms without reproduction, and mutation is a change within the same genome, not transfer. The correct answer is (D) Mutation.
Correct Answer
Horizontal gene transfer enables rapid bacterial evolution by acquiring foreign DNA through three main mechanisms: conjugation (direct cell contact via pili), transformation (uptake of free environmental DNA), and transduction (phage-mediated DNA packaging). Mutation, however, is an intracellular change like point mutations or frameshifts, not involving gene movement between cells.
Option Breakdown
| Option | Description | Why Correct/Incorrect |
|---|---|---|
| (A) Conjugation | Direct plasmid/chromosome transfer via sex pilus between bacteria (e.g., F-plasmid in E. coli). | Correct HGT. Requires cell-to-cell contact; spreads antibiotic resistance. |
| (B) Transformation | Competent bacteria uptake naked DNA from environment (e.g., Griffith’s pneumococcus experiment). | Correct HGT. Common in Streptococcus, Bacillus species. |
| (C) Transduction | Bacteriophages accidentally package and deliver donor bacterial DNA to recipients (generalized/specialized). | Correct HGT. P1 phage in E. coli is classic example. |
| (D) Mutation | Spontaneous or induced DNA sequence alterations within a single genome (e.g., UV-induced thymine dimers). | NOT HGT. No inter-organism transfer; vertical inheritance only. |
Microbial Genetics Relevance
HGT drives antibiotic resistance spread and virulence in pathogens, key for biotech exams. Distinguish from vertical transfer (parent to offspring) for MCQ success.
