1. Genetics of Viruses

2. Viral Structure n Virus: – “poison” (Latin) – infectious particles consisting of a nucleic acid in a protein coat n Capsid= viral envelope n Contain DNA or RNA n Bacteriophages (phages) are the most complex

3. Virus Diversity

4. Virus Reproduction n Host range – infection of a limited range of host cells (receptor molecules on the surface of cells) – West Nile- wide range (mosquitoes, birds, horses, humans) – Measles- narrow range (only humans)

5. Lytic Cycle n The lytic cycle: – attachment – injection – hydrolyzation – assembly – release n Results in death of host cell n Virulent virus (phage reproduction only by the lytic cycle)

6. Lysogenic Cycle n Genome replicated w/o destroying the host cell n Genetic material of virus becomes incorporated into the host cell DNA (prophage DNA) n Temperate virus (phages capable of using the lytic and lysogenic cycle) – Phage λ n May give rise to lytic cycle

7. Classes of Viruses

8. RNA viruses n Retroviruses: transcribe DNA from an RNA template (RNA  DNA) n Most complicated reproductive cycle n Reverse transcriptase (catalyzing enzyme) n HIV  AIDS

9. Reproduction of HIV

10. Vaccines and Emerging Viruses n Vaccines – Harmless versions of viruses – Helps immune system to build up antibodies for certain viruses n Emerging Viruses – Appear suddenly – AIDS, Ebola, SARS, H1N1

11. Viroids and Prions n Viroids: – tiny, naked circular RNA – infect plants – do not code for proteins, but use cellular enzymes to reproduce – stunt plant growth n Prions: – “infectious proteins” (mad cow disease) – trigger chain reaction conversions