In bacterial conjugation, the mechanism by which F+ bacteria transfer DNA to F- bacteria involves a relaxase enzyme. The relaxase function in conjugative transfer is:

• A Forming a pore in the pilus structure to allow double-stranded DNA transfer
• B Ligating the transferred ssDNA into a circular F plasmid after entry into recipient
• C Nicking the F plasmid at oriT, covalently attaching to the 5' end and unwinding DNA for transfer ✓
• D Synthesizing a complementary strand of transferred ssDNA in the donor cell

Explanation

Relaxase (TraI in F plasmid) is a trans-esterase that nicks the F plasmid at the specific site oriT (origin of transfer) creating a nick at nic site, covalently attaches to the 5' end of the nick via a tyrosine residue, and unwinds the DNA via its helicase activity; the 5'-attached relaxase-DNA complex (relaxosome) is transferred through the type IV secretion system (mating pore) into the recipient. DNA transfer is single-stranded with replacement strand synthesis occurring in both donor and recipient. The pilus mediates initial contact but DNA travels through the mating junction, not through the pilus lumen.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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