1. Big Questions: What is a virus? How does a virus function?
Viruses
Big Questions:
What is a virus?
How does a virus function?

2. What a virus is… “Obligate Intracellular Parasite” Composed of:
Cannot carry out life cycle independent of a cell host
Composed of:
Genome: DNA or RNA
Protein coat: Capsid
Host can be: any cell (prokaryote or eukaryote)

3. How big is a virus?

4. Prokaryotic Viruses PHAGES! (bacteriophages) 2 kinds:
Virulent phages: Lytic life cycle
Temperate phages: Lysogenic life cycle

5. Eukaryotic Viruses More diverse than phages
DNA or RNA genomes
Double or single stranded
Can have lipid envelope around protein coat
RNA viruses (retroviruses) mutations are very common, so permanent immunity not possible

6. Eukaryotic Viral Replication

7. HIV Life Cycle RNA viruses violate the Central Dogma!
Code or enzyme for Reverse Transcriptase
HIV destroys immune system cells (T-Helper) which leaves the body prone to opportunistic infections.
Drugs try to stop viral replication inside cell.
Ex: Protease inhibitors
Cost = $1200 month

8. Plant Viruses Plants get viruses too!
Look like “blotchy” pigment patterns

9. What viruses are not…
Viruses are not the most simple kinds of infections:
Viroids: Disease causing RNA molecules in plants
Prions: Disease causing protein molecules
Mad Cow, CJD in humans, scrapie (sheep)

10. Questions to answer!
Explain why viruses could be considered living or non-living depending on particular aspects of their function.
Explain how different types of viruses utilize the information system of cells to complete their life cycles.
Compare bacteriophages and eukaryotic viruses.
Compare lytic and lysogenic cycles of viral reproduction.
Explain the structure and function of HIV.
How do viral processes increase genetic variation in organisms?
Compare viruses to other infectious particles.