17. F-Plasmids in bacteria helps in-
(1) Transformation  (2) Transduction
(3) Conjugation       (4) Replication

F-plasmids in bacteria primarily facilitate conjugation, making option (3) the correct answer. This conjugative plasmid, also known as the F-factor, enables direct cell-to-cell transfer of genetic material via a sex pilus.​

Option Analysis

• (1) Transformation: This process involves bacteria taking up free naked DNA from the environment, not requiring plasmids like F for transfer. F-plasmids do not mediate this uptake.​

• (2) Transduction: Bacteriophages (viruses) carry bacterial DNA between cells during infection cycles. F-plasmids play no role in phage-mediated transfer.​

• (3) Conjugation: F-plasmids encode tra genes for pilus formation, rolling-circle replication, and single-strand DNA transfer from donor (F+) to recipient (F-) cells. This defines their core function in horizontal gene transfer.​

• (4) Replication: While F-plasmids replicate autonomously using their oriV, this supports maintenance, not the primary gene transfer role highlighted in the question.​

F-Plasmid Mechanism

The F-plasmid, about 100 kb, acts as an episome that can integrate into the bacterial chromosome, forming Hfr strains for higher recombination. During conjugation, oriT initiates nicking, and Tra proteins form a relaxosome for T-strand transfer through a type IV secretion system. Recipient cells synthesize complementary strands, gaining donor traits like antibiotic resistance.​