Is Cytomegalovirus a DNA or RNA virus?

• A. RNA
• B. DNA
• C. RNA-DNA hybrid
• D. Protein-only

Answer: (B)

Cytomegalovirus is a DNA virus. It’s a member of the herpesvirus family, and all herpesviruses have double-stranded DNA genomes. The CMV genome is linear dsDNA inside the capsid and is replicated in the host cell nucleus using a viral DNA polymerase. This nuclear DNA-based replication is a hallmark of DNA viruses.

Why that matters: if a virus has a DNA genome, its life cycle typically centers on DNA replication in the nucleus and uses DNA-dependent DNA polymerases. It isn’t an RNA virus, which would carry RNA as its genome and rely on RNA-dependent RNA polymerases, nor is it a RNA-DNA hybrid genome. It isn’t protein-only, since viruses carry nucleic acids to store genetic information.