The Nature of Viruses Chapter 27
Types of Viruses • DNA • RNA • Retroviruses
Main Shapes • Helical • Icosahedral
How Viruses Replicate • 1. Attach to and Enter Host Cell • 2. Take over Protein synthesis machinery inside of cell- Lysogenic Cycle • 3. Lytic Cycle- Lyse out of cell to go make more Virus Babies
Retroviruses • Use Reverse Transcriptase to make Viral RNA into DNA – HIV is a Retrovirus
Who can get a virus? • Just about every kind of organism • Obligate intracellular parasites • Host Range and Tissue Tropism • Hep- liver • Rabies-neurons • Chickenpox…..can you ever really get rid of it?
HIV • AIDS first reported in the US in 1981 • Originated in Africa in the 1950’s based on the rate of mutation • Closely related to a chimpanzee virus
Some people are resistant to HIVHow? • Recent research suggests that people who were immuned to smallpox may also be immuned to AIDS • Due to a mutation in CCR5 receptor • Makes virus unable to bind to cells and enter.
Treatments • Combination Drug Therapy • AZT and Protease inhibitors • Vaccine Therapy • Chemokines and CAF • Blocking CCR5
Other Viruses • Flu • Recombination vs mutation • Emerging viruses • Ebola • Sars • Hantavirus • Viruses can cause cancer
Prions and Viroids • Prions- misfolded protein • TSE’s are caused by prions • Why is this controvericial? • Viroids- infections RNA with no protein coat.