Q.81 Which of the following processes are involved in horizontal gene transfer (HGT)?
(i) Conjugation
(ii) Transduction
(iii) Binary fission
(iv) Transformation
(v) Translesion synthesis
(vi) Transversion
(A) (i), (iii), (iv) (B) (i), (iv), (vi)
(C) (ii), (iv), (v) (D) (i), (ii), (iv)
Horizontal gene transfer (HGT) involves the movement of genetic material between organisms other than by vertical inheritance from parent to offspring. The correct processes from the options are conjugation, transduction, and transformation. The answer is (D) (i), (ii), (iv).
Option Analysis
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(i) Conjugation: Direct cell-to-cell contact transfers plasmids or chromosomal DNA via a pilus, a key HGT mechanism in bacteria.
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(ii) Transduction: Bacteriophages carry bacterial DNA from one cell to another, either generalized or specialized.
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(iii) Binary fission: Asexual reproduction duplicates and divides DNA vertically to daughter cells, not HGT.
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(iv) Transformation: Competent bacteria uptake free environmental DNA and integrate it.
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(v) Translesion synthesis: Specialized polymerases bypass DNA lesions during replication for tolerance, not gene transfer.
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(vi) Transversion: Point mutation swapping purine for pyrimidine (e.g., A to C), unrelated to HGT.
Horizontal gene transfer processes enable bacteria to rapidly acquire new traits like antibiotic resistance through conjugation, transduction, and transformation. These mechanisms differ from vertical inheritance, playing a crucial role in microbial evolution and biotechnology.
Core HGT Mechanisms
Conjugation involves direct DNA transfer between bacteria via a sex pilus, often carrying plasmids with beneficial genes. Transduction uses bacteriophages to package and deliver bacterial DNA to new hosts. Transformation allows cells to take up naked DNA from the environment during competence.
Non-HGT Processes
Binary fission represents vertical gene transfer, producing identical daughters without inter-organism exchange. Translesion synthesis aids replication past DNA damage using error-prone polymerases. Transversion is a mutation type, not transfer, changing purine to pyrimidine bases.
