Examples of Viruses
Illustration of three viruses: the tobacco mosaic virus (TMV), the T4 bacteriophage,
and the Human Immunodeficiency Virus (HIV).
- Tobacco mosaic virus(TMV): consists of a single long RNA molecule
(6000 nucleotides) enclosed in a cylindrical protein coat (2130 copies
of the same coat protein). It is approximately 300 nanometers long and
15 nanometers wide.
- T4 bacteriophage: consists of a DNA molecule tightly packaged
in a protein head. The virus attaches to the surface of a bacteria cell
and injects its DNA into the cell through its tail.
- Human Immunodeficiency Virus (HIV): consists of an outer
lipid envelope derived from the host cell.
It is a retrovirus, i.e., an RNA-containing
virus that replicates by making a DNA intermediate.