Both repression and induction are examples of negative control since the repressor proteins turn off transcription. Images from W.H. Freeman and Sinauer Associates, used by permission. Plasmids carry between 2 and 30 genes. Some seem to have the ability to move in and out of the bacterial chromosome. An episome is a plasmid incorporated in the bacterial chromosome.
Plasmids are self-replicating in a manner like the bacterial chromosome.
Images from W.H. Freeman and Sinauer Associates, used by permission. The R plasmid conveys drug resistance on cells having it. As many as 10 resistance genes can be contained on a single R plasmid. The R plasmids can be transferred to other bacteria of the same species, to viruses, and even to bacteria of different species. In addition to the more common modes of transfer, R plasmids may be passed through the cell membrane.