Viruses

A virus is a sub-microscopic, obligate intracellular parasite - meaning it can only multiply inside a living host cell and is completely inert outside one. Structurally a virus is nothing more than a nucleic acid core (never both DNA and RNA together, only one or the other) wrapped in a protective protein coat. The very word 'virus' comes from the Latin for 'poison'. Because a virus genuinely displays some hallmarks of life and some hallmarks of non-life at the same time, it is often called a 'biological puzzle' that bridges the living and non-living worlds - and it is …