The donor cell maintains a functional copy of the plasmid. It later was discovered that the F factor was the first episome and can exist as an independent plasmid making it a very stable vector for cloning. Conjugation aids in the formation of bacterial clone libraries by ensuring all cells contain the desired fosmid.
The donor cell retains a functional copy of the plasmid, which can be used to create bacterial clone libraries. The discovery that the F factor is an independent plasmid makes it a very stable vector for cloning. Conjugation is used to ensure all cells in the library contain the desired fosmid.