In general, viruses contain solely one kind of nucleic acid (either DNA or RNA) that consists of the statistics imperative for viral replication. Nevertheless, it is clear now that some viruses contain other nucleic acid molecules; for example, in retroviruses, cellular transfer RNAs are fundamental for the motion of the enzyme reverse transcriptase. The chemical composition of viruses varies between one of a kind virus families. For the simplest of viruses, the virion is composed of viral structural proteins and nucleic acid, but the state of affairs becomes extra complicated with the enveloped viruses. The latter kinds of viruses are maturing through budding through specific mobile membranes that are modified by the insertion of viral proteins.