Viruses are found everywhere, very small, nucleoprotein particles. They might have played role in origin of life on prebiotic earth. They are non-living particles outside living cell and are obligatory parasites. They cause number of diseases of plants, animals and kill bacteria.
Nucleoprotein particles consists of genetic material, either DNA or RNA enclosed in protein capsids.
Virus enters a host cell and hijack their metabolic machinery to synthesize their own proteins and duplicate their genetic material to multiply. Their exact copies are encoded in their genetic material.
The new coronavirus SARS-CoV-2, aka the Covid-19 virus, is fairly typical. Like about 65 per cent of known viruses its genome is made of RNA (the rest have a DNA genome), which encodes four structural proteins. One of these forms the capsid and the others are components of a double envelope. One of them, the spike protein, is used to break into its host’s cells.