sex factor

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sex factor A plasmid found in the cytoplasm of certain bacteria that is responsible for initiating conjugation and gene transfer. The sex factor in Escherichia coli is known as the F factor; it can be transferred from a donor cell (F+) to a recipient (F) by conjugation. Occasionally the F factor may become integrated with the chromosome of an F+ bacterium to form a high-frequency recombinant (Hfr) cell. This enables the part of the host chromosome nearest to the F factor to be transferred to the recipient by conjugation.