The F Factor

F factor is a transfer factor it contains the genetic information necessary for the synthesis of sex pilus and for self-transfer but it do not have informations like drug resistance.

Cells carrying the F factor (F+ cells) have no distinguishing features other than their ability to mate with F- cells.

The F factor is actually an episome and have the ability to exist in some cells in the ‘integrated state’ or inserted into the host chromosome.


a genetic element inside some bacterial cells, especially the DNA of some bacteriophages, that can replicate independently of the host and also in association with a chromosome with which it becomes integrated.

Such cells are able to transfer chromosomal genes to recipient cells with high frequency and are called Hfr cells. After conjugation with an Hfr cell, F- rarely become F+, though it receives chromosomal genes from the donor.

F Prime Factor

The conversion of F+ cell into the Hfr state is reversible. When the F factor reverts from the integrated state to the free state, it may sometime carry with it some chromosomal genes is called an F (F’) prime factor. When an F’ cell mates with a recipient, it transfers, along with the F factor. The host gene incorporated with it.


The process of transfer of host genes through the F’ factor resembles transduction and has therefore been called sexduction.

Gaurav Singh

Editor in Chief Medical Microbiology & RDT Labs - RDT Labs Magazine | BSc Medical Microbiology | MSc Microbiology

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