1. Viruses
AP Biology
Ch & 18.2

2. Viruses
Smallest biological particles capable of causing disease in living organisms

3. Virus Structure
Nucleic Acid (DNA or RNA)
Protein Coat (Capsid)

4. Virus Function Infection & Replication: Bacteria: Bacteriophage virus
Archaea: Sulfolobus virus STSV1
Protists: Cafeteria roenbergensis virus
Fungi: Cryphonectria parasitica hypovirus 1

5. Infecting Plants
1630’s Holland
“Tulip Mania”
Tulip breaking virus

6. Infecting Animals Gypsy Moth Caterpillar Baculovirus
Forage at night, hide during the day
Baculovirus
Climb, Die, Liquefy:
Drip infected globs onto lower branches

7. Infecting Humans

8. 1918 Spanish Flu
~50,000,000 people died

9. Infecting Viruses
Sputnik virophage infecting a mamavirus

10. And yet, viruses are not alive
Genetic Code: Yes
Reproduce: Need Host
Evolve: Need Host
Metabolism: No
Cellular Organization: No
“Organisms on the edge of life”

11. Virus Genetic Code dsDNA: Herpes ssDNA: Bacteriophages
dsRNA: Rotavirus
ssRNA: Influenza

12. Viral Replication Attachment Endocytosis Uncoating Replication
Self Assembly
Exocytosis

13. Youtube

14. Virus Diversity & Evolution
Small Viruses: 2000 nitrogen bases (2 proteins)
Large Viruses: 1,000,000 nitrogen bases (1000s proteins)

15. Viral Evolution Past Origin of viruses?
Viruses do not leave behind fossils

16. Evidence: Natural History
Current viruses need host cells to live
Cell life began 3.5bya
Viruses independently evolved ~3.5bya?

17. Virus: Diversity
Viruses have evolved alongside life for 3.5 by

18. Viral Evolutionary Trade-offs
Viruses are usually:
Host specific
Not life threatening

19. Creating Vaccines Create an inactive form of virus (capsid)
Immune system recognizes future virus

20. Flu Virus Mutations

21. Tracking Virus Evolution
Viruses constantly evolve:
rapid reproduction
Millions of copies in hours
high mutation rates
No proofreading mechanism

22. Review: Your Genome DNA (genotype)  RNA  protein (phenotype)
23 pairs of chromosomes
~3,000,000,000 nitrogen bases
Only 1.5% DNA codes for protein

23. Viruses in your genome French scientists: Fora.tv Carl Zimmer
Cut out noncoding human DNA
Inserted into DNA into a cell
Made viral protein
Fora.tv Carl Zimmer
~ 8% of your DNA is viral DNA

24. Virus pandemics Viruses that spread throughout large populations
2009: H1N1 “swine flu” pandemic
600,000 people infected
8,000 fatalities
1997: H5N1 “avian flu”
18 people infected
6 people died

25. Further out on the edge…
Viroids:
infectious RNA in plants: “apple scar viroid”
Prions:
infectious proteins in mammals: “mad cow”