Question

Which of the following can be used as a measure to construct a linkage map of the Hfr chromosome?

• A. Frequency of recombination
• B. Time of entry
• C. Locus of mutation
• D. Transfer of F factor

Hint:

In Hfr conjugation, the order of gene transfer can help create a precise genetic map, revealing how closely genes are linked on the chromosome.

Answer 1

The Correct Option is B

In Hfr (high-frequency recombination) strains of bacteria, genes are transferred from the Hfr chromosome to the recipient chromosome during conjugation. The time of entry of various genes during this process can be used to map their relative positions on the chromosome. The order in which genes are transferred indicates their relative distances from each other.

(1) Time of Entry:
- The time of entry of genes during conjugation can be measured, and this information is used to construct a linkage map of the Hfr chromosome. The closer two genes are on the chromosome, the closer they will be in terms of the time at which they enter the recipient cell during conjugation.

(2) Why Other Options Are Incorrect:
- Frequency of recombination (Option 1) is important in genetic mapping but does not specifically provide the timing information needed for an Hfr map.
- Locus of mutation (Option 3) refers to the location of mutations but does not provide direct information about gene transfer or linkage mapping.
- Transfer of F factor (Option 4) refers to the transfer of the fertility factor but does not directly relate to constructing a linkage map of the Hfr chromosome.

Conclusion: The time of entry of genes during conjugation is the best method to construct a linkage map of the Hfr chromosome, as it provides the necessary information about the order and distance of genes.