ABSTRACT
Viruses are small – too small to be seen using a light microscope. The mature virus particle (virion) consists of nucleic acid (the genome) surrounded by a protective protein coat (the capsid). Some viruses also have an outer lipid envelope. Viruses are metabolically inert and are referred to as obligate intracellular parasites. Replication involves independent synthesis of component parts followed by assembly into new virus particles.
