In bacterial conjugation, what is the essential property of a donor strain ?
Show Hint
- F-plasmid
- Flagella
- Capsule layer
- Lipoproteins
The Correct Option is A
Solution and Explanation
Bacterial conjugation is a mechanism of horizontal gene transfer where DNA is transferred from a donor bacterium to a recipient cell through direct physical contact.
Step 2: Detailed Explanation:
During conjugation, the donor cell is called the F${}^+$ (male) strain, and the recipient is the F${}^-$ (female) strain.
The essential property of a donor strain is the presence of the F-plasmid (Fertility factor).
The F-plasmid is an extrachromosomal DNA molecule that contains genes (the *tra* operon) responsible for:
- Producing a specialized, hollow protein appendage called the sex pilus.
- Establishing physical contact and forming a conjugation bridge with the recipient F${}^-$ cell.
- Initiating rolling-circle replication to transfer a single-stranded copy of the plasmid DNA to the recipient.
Without the F-plasmid, a bacterial cell cannot form a sex pilus or initiate conjugation, making it ineligible to act as a donor strain.
Flagella are used for swimming motility, capsules protect against phagocytosis, and lipoproteins are membrane structural components, none of which drive conjugation.
Step 3: Final Answer:
The essential property of a donor strain in conjugation is the F-plasmid, which corresponds to option (A).
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