Viruses, Prions, and Viroids (Oh my)

What is a virus? They are obligate intracellular parasites. They contain either RNA (retrovirus) or DNA. The have a protein coating and sometimes lipids. They have the ability to take over the metabolic capabilities of cells in order to replicate and evolve. Viruses are derived from their hosts and are more closely related to them, than to each other.

How do viruses replicate? Viruses must use the host cell to replicate Cannot replicate on their own because they’re not alive Viruses can be lytic, lysogenic, or both

The Lytic Cycle Invade cells and use the cell’s machinery to make more viruses When the virus is done replicating it causes the host cells to “lyse” or burst and the new viruses emerge to invade new cells Example: the common cold

The lysogenic cycle Lysogenic viruses keep their hosts alive. The virus is able to combine it’s genetic material with that of the host. Often the host cell will demonstrate notable differences (phage conversion). Example: bacteriophages

Vaccines The creation of the vaccine: Edward Jenner 1790 Cow pox vs. Small pox Vacca = Vache = cow 1980 the World Health Organization (WHO) announced the eradication of small pox. The last case was in 1978.

Viroids “naked” genetic material Found in plants Meaning what? Found in plants Cause errors in the regulatory system of plants

Prions Prions are parts of a protein- have no genetic material Example: Mad Cow Disease, Sheep scrapie, Creutzfeldt-Jakob Disease- 9 total All cause spongiform encephalopathies (large holes in the brain) If prions don’t have nucleic acid how can they be a transmissible pathogen?