Which of the following is NOT a broad mechanism that mediates efficient movement of DNA between cells?

Appeared in: AIIMS BBSR SNO - 2019

Explanation

Mutation is defined as a random, heritable alteration in the nucleotide sequence of an organism's genome.
This change occurs within a single cell and is passed down to its progeny (vertical transfer), but it is not a mechanism for transferring DNA to another existing cell (horizontal transfer).
Therefore, it is the exception among the given options, as it does not mediate the movement of DNA between cells.

Option A: Transduction is a primary mechanism of horizontal gene transfer where a bacteriophage (a virus that infects bacteria) acts as a vehicle to carry DNA from a donor bacterium to a recipient bacterium.
Option C: Transformation is a process where a bacterial cell takes up naked DNA fragments from the surrounding environment and incorporates them into its own genome. This is a form of DNA movement into a cell.
Option D: Conjugation is the transfer of genetic material, typically a plasmid, between bacterial cells through direct cell-to-cell contact, often involving a structure called a pilus. It is a major mechanism for spreading genes between bacteria.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanisms of horizontal gene transfer in bacteria as background academic context rather than a clinical decision trigger.
The mechanisms of horizontal gene transfer (conjugation, transduction, transformation) are clinically significant because they are the primary ways that antibiotic resistance spreads among bacterial populations.
Conjugation is particularly important in healthcare settings as it can rapidly transfer multi-drug resistance plasmids between different species of bacteria, leading to the emergence of 'superbugs'.
A nurse's understanding of these concepts underpins infection control practices and antibiotic stewardship programs, which aim to limit the spread of resistant organisms.

How to Approach the Question

First, identify the negative keyword 'NOT' in the question stem. This signals that you must find the option that is the exception.
The question asks about the 'movement of DNA between cells'. This refers to horizontal gene transfer.
Review each option's definition in the context of bacterial genetics.
Transduction: DNA transfer via a virus. This is movement between cells.
Transformation: Uptake of DNA from the environment. This is movement into a cell.
Conjugation: DNA transfer via direct contact. This is movement between cells.

Concept Tested & Keywords

Concept Tested: Mechanisms of horizontal gene transfer in bacteria
Stem keywords: DNA movement, between cells, mechanism
Lead-in keywords: NOT
Negative lead-in flag: The question asks for the option that is NOT a mechanism of DNA transfer.

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E6 Microbiology Essentials Sastry 4e Part 1 pp. 66-68, 67-69, 69-71

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