The Fertility factor (also known as F factor or sex factor) is a bacterial DNA sequence that allows a bacterium to prouce a sex pilus necessary for conjugation. It contains 20 tra (for "transfer") genes and a number of other genetic sequences responsible for incompatibility, replication, and other functions. The F factor is an episome and can exist as an independent plasmid or integrate into the bacterial cell's genome. There are several names for the possible states: