Final answer:
The number of bacterial genes transferred during conjugation depends on the duration the conjugation pilus connects the two cells. Genes closer to the F plasmid integration site are transferred faster than those farther away. The time it takes to transfer a gene can be used to map the bacterial genome.
Step-by-step explanation:
The number of bacterial genes transferred during conjugation depends on the duration the conjugation pilus, also known as a sex pilus, remains intact and connects the donor and recipient cells.
In E. coli, the process of conjugation involves a donor F+ cell forming an F pilus that connects to an F- recipient cell, enabling the transfer of DNA, which could be an F plasmid or part of the bacterial chromosome if the F plasmid is integrated into it (Hfr cell). This happens through a mechanism known as rolling circle replication.
As transfer is initiated, DNA material closest to the integration site of the F plasmid begins to get displaced, and therefore, this DNA is transferred first. Depending on how long the conjugation process remains uninterrupted, more distal genes will be sequentially transferred.
However, since the entire bacterial chromosome is quite large and the conjugation process may be disrupted before it is fully transferred, only a segment of DNA is usually transferred.
This allows for genes located near the F plasmid integration site on the Hfr cell's chromosome to be transferred to the recipient more readily than genes located farther away.
Furthermore, the length of DNA that is transferred also provides information about the size of the transferred genes as longer genes require more time to be transferred completely.