Question

Which one of the following is correct in the case of conjugation of a high frequency recombination (Hfr) strain with F- strain of E. coli?

• A. Recombination frequency is high, F factor transfer frequency is low
• B. Recombination frequency is high, F factor transfer frequency is high
• C. Recombination frequency is low, F factor transfer frequency is high
• D. Recombination frequency is low, F factor transfer frequency is low

Answer 1

The Correct Option is A

To solve the question and determine the correct answer, we need to understand the process of bacterial conjugation specifically involving a high-frequency recombination (Hfr) strain and an F- strain in E. coli.

Background: Bacterial conjugation is a process by which one bacterium transfers genetic material to another through direct contact. There are different types of strains involved in conjugation:

• F+ strain: Carries the F (fertility) plasmid and can initiate conjugation.
• F- strain: Lacks the F plasmid and can receive genetic material.
• Hfr strain: The F factor is integrated into the bacterial chromosome, allowing it to transfer chromosomal genes to an F- strain with high recombination frequency.

During conjugation with an Hfr strain:

1. The Hfr strain makes contact with the F- strain and transfers part of its DNA, including some chromosomal genes.
2. Due to the integrated nature of the F factor in the Hfr strain, the transfer often begins within the chromosomal DNA.
3. During conjugation, the part of the F factor is the last to be transferred. However, conjugation is usually interrupted before the entire chromosomal DNA and the complete F factor can be transferred.

Conclusion: As a result:

• Recombination Frequency: High, because the Hfr strain transfers chromosomal genes with high recombination potential to the F- strain.
• F Factor Transfer Frequency: Low, because the entire F factor is rarely successfully transferred during the conjugation process.

Thus, the correct answer is:

Recombination frequency is high, F factor transfer frequency is low