Question

Which one of the following conjugations will result in formation of merodiploids?

• A. F$^+$ donor $\times$ F$^-$ recipient
• B. Hfr donor $\times$ F$^-$ recipient
• C. F$^\prime$ donor $\times$ F$^-$ recipient
• D. None of the above

Hint:

Merodiploids are formed specifically in F$^\prime$ conjugation because the F plasmid carries extra chromosomal genes, giving the recipient partial diploidy.

Answer 1

The Correct Option is C

Step 1: Definitions
- Merodiploid: A bacterial cell carrying two copies of a chromosomal region (partial diploidy). This arises when extra chromosomal DNA (plasmid or F$^\prime$ factor) carries a portion of the bacterial chromosome.
Step 2: Analyze options
(A) F$^+$ $\times$ F$^-$: Transfer of only the F plasmid, no chromosomal genes. No merodiploid formation.
(B) Hfr $\times$ F$^-$: Chromosomal DNA transfer occurs, but integration requires recombination, not stable merodiploidy.
(C) F$^\prime$ $\times$ F$^-$: The F$^\prime$ factor contains plasmid + extra bacterial chromosomal genes. After transfer, the recipient cell receives a second copy of those chromosomal genes $⇒$ becomes a merodiploid.
(D) None of the above – Incorrect, since (C) is correct.
Step 3: Conclusion
The conjugation between an F$^\prime$ donor and an F$^-$ recipient produces merodiploids.