The first two are common to all viruses:
1. Nucleic acid core. The nucleic acid core can either be DNA or RNA that makes up the genetic information of the virus. RNA genome only occurs in viruses.
2. Capsid. A capsid is the protein coat that protects the nucleic acid from the environment. It also plays a role in how some viruses attach to a host cell.
Some have an
3. Envelope. An envelope is a membrane bilayer outside their capsid. If a virus does not have an envelope, the virus is called a naked virus. A naked virus is more resistant to changes.