Virus Characteristics -Viruses are not considered alive as they do not have a metabolism or reproduce on their own. -Viruses are composed of DNA or RNA surrounded by a protein coat called a capsid. -If viruses are composed of RNA as their genetic material, they are called retroviruses

Viral Reproduction: -In the lytic cycle, a virus enters a cell and makes copies of itself that causes the cell to burst. ANIMATION! http://www.pgl.ufl.edu/modules/mysterious_invaders/lytic.htm

-In the lysogenic cycle, a virus integrates its DNA into the DNA host cell, and the viral genetic information replicates along with the host cell’s DNA. They do not lyse the host cell right away. ANIMATION! http://www.pgl.ufl.edu/modules/mysterious_invaders/lytic.htm

Viral Disease Like bacteria, viruses also can cause disease by disrupting the body’s normal equilibrium. -Unlike bacterial diseases, antibiotics do NOT work on viruses. -A vaccine can be used to prevent a viral disease.

-Some viruslike particles have been discovered that also can cause disease. -One example is a prion which is a protein infectious particle and contains no DNA or RNA (only protein!). This was found to be the culprit in mad cow disease.