Answer:
The fertility factor or the F factor signifies a plasmid in some bacteria, which allows the conduction of genetic substance from a donor cell to the recipient by the process of conjugation, leading to recombination.
The genotypic difference between the F- cells, F+ cells, and the Hfr cells are that the F- cells are devoid of the F factor, the F+ cells possess autonomous F factor, that is, a segment of DNA, which can replicate autonomously in the cell. In case of Hfr, the F factor is integrated into its chromosomal DNA, thus, they carry an integrated F factor.