In conjugation genetics, chromosomal genes associated with an integrated fertility factor are collectively characteristic of which bacterial state?
-
AR factor
-
BF prime factor
-
CHFr
-
DF factor
Answer
Correct Answer: HFr
Explanation
Introduction / Context:The fertility (F) factor in E. coli can exist as a plasmid or integrate into the chromosome. When the F factor is integrated, the cell is termed HFr (High-frequency recombination) because chromosomal DNA is efficiently transferred during conjugation. This concept is central to classical bacterial mapping.
Given Data / Assumptions:
- F factor is present in association with chromosomal genes.
- Focus is on the cellular state name.
Concept / Approach:HFr cells result from site-specific recombination of the F factor into the chromosome. During mating, transfer begins at oriT in the integrated F, so extensive chromosomal regions can be transferred to the recipient.
Step-by-Step Solution:
1) Distinguish F states: F+ (free plasmid), HFr (integrated), F′ (F prime carrying chromosomal genes), R factor (resistance plasmid).2) The prompt states chromosomal genes with fertility factor → HFr.3) Choose HFr.Verification / Alternative check:HFr mapping experiments (minutes map) historically defined gene order by interrupted matings, confirming the definition.
Why Other Options Are Wrong:
- R factor: Resistance plasmids; not necessarily fertility related.
- F factor: Free, not integrated.
- F prime factor: F plasmid that excised aberrantly and carries some chromosomal genes; distinct from HFr.
Common Pitfalls:
- Confusing F′ with HFr; F′ is plasmid-borne with extra genes, whereas HFr is integrated.
Final Answer:HFr