Viruses AP Biology Ch. 18.1 & 18.2

Viruses Smallest biological particles capable of causing disease in living organisms

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

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

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

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

Infecting Humans

1918 Spanish Flu ~50,000,000 people died

Infecting Viruses Sputnik virophage infecting a mamavirus

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”

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

Viral Replication Attachment Endocytosis Uncoating Replication Self Assembly Exocytosis

Youtube http://www.youtube.com/watch?v=Rpj0emEGShQ

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

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

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

Virus: Diversity Viruses have evolved alongside life for 3.5 by

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

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

Flu Virus Mutations

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

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

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

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

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