Final answer:
It takes about 100 minutes for an entire Hfr cell chromosome to be transferred to an F- cell, but the complete transfer is rare due to the transient nature of bacterial conjugation. Gene transfer timing is used to map bacterial genomes and reflect gene sizes.
Step-by-step explanation:
The transfer of the entire chromosome from an Hfr cell to an F- cell can take approximately 100 minutes in the bacterial species E. coli. However, due to the transient nature of conjugation between bacterial cells, it is unusual for the complete chromosome to be transferred. Instead, the process is often interrupted before the entire sequence is delivered. During conjugation, a single strand of bacterial chromosomal DNA is nicked at the original insertion site of the F plasmid and begins to transfer to the recipient F- cell. This transfer occurs through a rolling circle replication process.
Genes closest to the integration site are transferred more readily, which has historically been exploited to create genomic maps of bacteria before the advent of genome sequencing technologies. The timing of gene transfer during conjugation is also reflective of gene size and can determine linear gene arrangements on the bacterial DNA.