The Nature of Viruses Chapter 27.
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Transcript of The Nature of Viruses Chapter 27.
The Nature of Viruses
Chapter 27
Structure of Viruses
Types of Viruses
• DNA• RNA• Retroviruses
Main Shapes
• Helical
• Icosahedral
Sizes of Viruses
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.
How the HIV Infection Works
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.