However, as a group. DNA viruses vary greatly in the way their genomes are replicated. Some viruses such as SV40 depend heavily on the host replication system, and have only one or a few replication factors encoded by the viruses. Other viruses such as herpes simplex viruses have an almost complete set of viral replication factors,and use strategies totally different from the chromosomal replication of their host cells. The genomic replication of some DNA viruses such as baculoviruses appears to be relatively independent of phases of the host cell cycle, while that of others such as Epstein-Bar virus during latency is very well coordinated with the proliferation of host cells. Different strategies in genome replication may require discrete regulatory mechanisms for replication initiation.