Viruses and prions.. Genetic material in viruses is similar to cellular genes. A non-living band of genetic material is surrounded by a protein membrane, which does not multiply spontaneously and invades living cells

The virus is an inanimate band of genetic material surrounded by a protein that does not multiply on its own, invades living cells and causes diseases.
The size of the virus: is the smallest structures causing the disease and see only the strongest electronic microscopes, ranging in size between 5 300 nm.
* The origin of viruses: The most likely theory is that viruses originated from cells (genetic material is similar to cellular genes).
* Virus installation:
1- DNA (genetic material): either DNA or RNA.
2- protein envelope (wallet): surrounds the DNA.