Which option lists all three classical mechanisms of horizontal gene transfer in bacteria?

Which option lists all three classical mechanisms of horizontal gene transfer in bacteria?

• A. Mutation, selection, recombination
• B. Binary fission, sporulation, germination
• C. Transcription, translation, replication
• D. Transformation, transduction, conjugation

Answer: (D)

Horizontal gene transfer in bacteria occurs through three classic mechanisms that move DNA between organisms: transformation, where cells take up naked DNA from their surroundings; transduction, DNA is moved from one bacterium to another via bacteriophages; and conjugation, DNA is transferred through direct cell-to-cell contact often mediated by a sex pilus and plasmids. These pathways let bacteria acquire new traits, such as antibiotic resistance, independent of reproduction. The other options describe processes that are not routes of DNA exchange: mutation and selection are evolutionary forces acting on variation; and transcription, translation, and replication are steps in gene expression and DNA copying, not methods of DNA transfer between cells. So transformation, transduction, and conjugation are the three classical horizontal gene transfer mechanisms.

Horizontal gene transfer in bacteria occurs through three classic mechanisms that move DNA between organisms: transformation, where cells take up naked DNA from their surroundings; transduction, DNA is moved from one bacterium to another via bacteriophages; and conjugation, DNA is transferred through direct cell-to-cell contact often mediated by a sex pilus and plasmids. These pathways let bacteria acquire new traits, such as antibiotic resistance, independent of reproduction. The other options describe processes that are not routes of DNA exchange: mutation and selection are evolutionary forces acting on variation; and transcription, translation, and replication are steps in gene expression and DNA copying, not methods of DNA transfer between cells. So transformation, transduction, and conjugation are the three classical horizontal gene transfer mechanisms.