The
Fertility factor (first named
F by one of its discoverers
Esther Lederberg) allows genes to be transferred from one bacterium carrying the factor to another bacterium lacking the factor by
conjugation. The F factor is carried on the F
episome, the first episome to be discovered. Unlike other plasmids, F factor is constitutive for transfer proteins due to the gene
traJ. The F plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system.