Final answer:
Conjugation is the event required for genes on an Hfr chromosome to be transferred onto the recipient cell's chromosome. Hfr cells treat the bacterial chromosome like an enormous F plasmid and attempt to transfer a copy of it to a recipient F-cell. During conjugation, host chromosomal DNA near the integration site of the F plasmid is more likely to be transferred and recombined into the recipient cell's chromosome.
Step-by-step explanation:
The event that is required for genes on an Hfr chromosome to be transferred onto the recipient cell's chromosome is conjugation. Hfr cells, which are high-frequency recombination cells, treat the bacterial chromosome like an enormous F plasmid and attempt to transfer a copy of it to a recipient F- (F-negative) cell. During conjugation, the unidirectional process of rolling circle replication displaces host chromosomal DNA near the integration site of the F plasmid, making it more likely to be transferred and recombined into the recipient cell's chromosome. This allows for the transfer of chromosomal DNA from the Hfr donor cell to the recipient cell.