A lysogen or lysogenic phage is a phage that can exist as a prophage within its host organism. A prophage is the phage DNA in its ormant state, and is either integrated into the host bacteria's chromosome or more rarely exists as a stable plasmid within the host cell. The prophage expresses gene(s) that repress the phage's lytic action, and the phage enters the lytic cycle when this suppression is disrupted. Currently a variety of studies are being conducted to see whether other genes are active during lysogeny, examples of which include phage-encoded tRNA and virulence genes.