Bacteriophages
Certain types of viruses replicate by the lysogenic cycle, but also partly by the lytic cycle (mixed cycles). Some DNA phages, called temperate phages, only lyse a small fraction of bacterial cells; in the remaining majority of the bacteria, the phage DNA becomes integrated into the bacterial chromosome and replicates along with it. In this lysogenic state, the information contained in the viral nucleic acid is not expressed. The model organism for studying lysogeny is the lambda phage. Roughly 50-60 nucleotides are taken out of the lysogenic pathway and used.
Read more about this topic: Lysogenic Cycle