1) The lambda bacteriophage can enter either the lytic cycle or lysogenic cycle in infected E. coli cells. 2) In the lysogenic cycle, the phage genome integrates into the bacterial chromosome as a prophage and is replicated as the bacterium divides. The phage repressor protein binds to operator sites to repress transcription of lytic genes. 3) In the lytic cycle, the phage immediately begins replicating and producing virion proteins to assemble new phage particles, eventually causing lysis of the host cell. The phage Cro protein competes with the repressor to bind operator sites and activate transcription of lytic genes.