A virus is a submicroscopic infectious particle that can replicate only inside the living cells of an organism. Virus particles outside a host cell, or “virions,” consist of two or three parts:
- the genetic material (red) made from either DNA or RNA
- a protein coat (green) that protects these genes, and in some cases
- an envelope of lipids (gray) and proteins (orange) that surrounds the protein coat.
Virions, though diverse in size and shape, can be categorized into one of the following predominate morphotypes: polyhedral (e.g., icosahedral), helical, enveloped or complex (e.g., bacteriophage).
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Image Credit: Nossedotti (Anderson Brito) / Wikimedia Commons.
