Conjugation involves which mode of DNA transfer?

• A. Transfer via virus
• B. Direct transfer of DNA from one bacterial cell to another
• C. Uptake of DNA from the environment
• D. Gene transfer by transformation

Answer: (B)

Conjugation is the direct transfer of genetic material from one bacterial cell to another through physical contact, usually via a sex pilus from a donor cell carrying the F plasmid. This direct connection allows DNA—often a plasmid, and sometimes chromosomal DNA from the donor in special cases—to move into the recipient, changing its genetic makeup. It requires the donor to have a fertility factor (like the F plasmid) and the two cells to be in contact; without that contact, conjugation can’t occur. This is different from other DNA transfer methods: transduction uses a virus to move DNA between cells, and transformation involves uptake of naked DNA from the surrounding environment by a competent cell. So the mode described is the direct, cell-to-cell transfer of DNA, i.e., conjugation.