Answer :
Final answer:
Hfr conjugation, which involves high frequency of recombination, occurs in conjunction with an F- strain whereby part of the chromosomal DNA of a donor Hfr cell is transferred to a recipient F- cell during conjugation. The closer the genes are to the integration site of the F plasmid in the Hfr cell, the higher the chances of them being transferred. An Impricise excision of the F plasmid from the chromosome can transform an Hfr cell into an F' cell.
Explanation:
Hfr conjugation in bacteria, such as E. coli, occurs with an F- strain. The wording Hfr ('High-Frequency of Recombination') refers to a particular type of bacterial cell where the F plasmid (Fertility factor) has been incorporated into the chromosomal DNA of the bacteria. These Hfr cells have a high frequency of gene transfer during conjugation due to the gene exchange capacity provided by the integrated F plasmid.
During an Hfr-F- mating, the donor Hfr cell can transfer part of its chromosomal DNA, which begins immediately adjacent to the F plasmid integration site, to the recipient F- cell. The transfer is however rarely complete because the entire chromosome transfer process takes a long time and the physical contact between the donor and recipient cells during conjugation is usually short-lived. But genes closer to the F plasmid integration site have a higher probability of being transferred and potentially recombined into the recipient F-cell's chromosome, hence the high recombination frequency.
It's important to note that an Hfr cell can also revert to an F+ cell or transform into an F' cell (a cell with a plasmid carrying both F and chromosomal genes) if the F plasmid is excised imprecisely from the chromosome. Whether maintained as part of the F' plasmid or recombined into the recipient cell's chromosome, this DNA, upon conjugation, can introduce recipient cell to new genetic material.
Learn more about Hfr conjugation here:
https://brainly.com/question/32811233
#SPJ11
