Graphics Gallery - Illustration of three 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.