IMMUNOLOGY

Detailed explanation-1: -The simplest virions consist of two basic components: nucleic acid (single-or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.

Detailed explanation-2: -DNA viruses are divided into three major categories: double-stranded (ds) DNA viruses (e.g., poxviruses), single-stranded (ss) DNA viruses (e.g., parvoviruses), and pararetroviruses (e.g., hepadnaviruses).

Detailed explanation-3: -All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. Some viruses are also enclosed by an envelope of fat and protein molecules. In its infective form, outside the cell, a virus particle is called a virion.