Explain the chemical structure of viruses.

Viruses are small nucleocapsids.
* Contains either DNA or RNA but not both, as their genetic material.
* Genetic material surrounded by protein coat is called as capsid.
* Capsid is made of protein subunits called as capsomeres.
* Generally plant viruses contains ssRNA as genetic material.
* Generally animal viruses contains dsDNA as genetic material.
* Viral nucleic acids are either circular or linear.
* Symmetry of capsid decides the shape of virus. Helical virus : Eg: TMV