What are the three main modes of horizontal gene transfer in bacteria?

• A. Transformation, Transduction, Conjugation
• B. Mitosis, Meiosis, Binary fission
• C. Transcription, Translation, Replication
• D. Osmosis, Diffusion, Filtration

Answer: (A)

Bacteria exchange genes laterally through three main routes: transformation, transduction, and conjugation. Transformation happens when a cell takes up free DNA from its environment and may incorporate that DNA into its own genome, potentially gaining new traits. Transduction occurs when a bacteriophage carries DNA from one bacterium to another during infection, spreading genetic material between cells. Conjugation is a direct transfer of DNA between two adjacent bacteria, usually via a pilus that forms a bridge to move genetic material, such as plasmids or parts of the chromosome.

These are distinct from other cellular processes: mitosis and meiosis (and even binary fission in bacteria) are about cell replication and division rather than exchanging genes between organisms; transcription, translation, and replication are steps in gene expression and DNA copying; and osmosis, diffusion, and filtration are membrane transport processes.