Start-up entities in the origin of new genes.

The remarkable diversity in the contents of genomes raises questions about how new genes and new functions originate. Recent evidence indicates that parasitism, particularly the molecular interactions between phage and their bacterial hosts, is a likely mechanism for generating new genes. This invention of such novel functions seems to be founded on a strategy that secures the short-term survival of parasitic elements and thereby contributes to the renovation of gene repertoires in their host.