Introduction to DNA Viruses

The genomes of DNA viruses are replicated by either host or virally encoded DNA polymerases. There is considerable diversity among DNA virus genomes and the relative stability of DNA allows for genomes much larger than possible for RNA viruses. Genomes of DNA viruses that infect animals range in size from less than 2 kb of single-stranded DNA to over 375 kb of double-stranded DNA. There are even larger DNA viruses that infect eukaryotic microorganisms. The genomes of DNA viruses vary in structure, size, and genome structure thus replication strategies are diverse. A feature common to many DNA viruses is their dependence on host DNA replication to provide enzymes (for example, DNA polymerases) and the deoxynucleotide triphosphate precursors required for DNA synthesis.