1. Chapter 19

2.  The components of a virus.  The differences between lytic and lysogenic cycles.

3. BacteriaVirus  Prokaryotic cell  Most are free-living (some parasitic)  Relatively large size  Antibiotics used to kill bacteria  Not a living cell (genes packaged in protein shell)  Intracellular parasite  1/1000 size of bacteria  Vaccines used to prevent viral infection  Antiviral treatment

4. Viruses  Very small (<ribosomes)  Components = nucleic acid + capsid Nucleic acid: DNA or RNA (double or single-stranded) Nucleic acid: DNA or RNA (double or single-stranded) Capsid: protein shell Capsid: protein shell Some viruses also have viral envelopes that surround capsid Some viruses also have viral envelopes that surround capsid  Limited host range (eg. human cold virus infects upper respiratory tract)  Reproduce within host cells

6. Mantra? Define it! Explain it! Give an example!

8. Simplified viral replicative cycle

9. Bacteriophage  Virus that infects bacterial cells

10. VIDEO: T4 PHAGE INFECTION T4 PHAGE INFECTIONT4 PHAGE INFECTION Watch this!

11. Lytic Cycle of T4 Phage

12. Bacteriophage Reproduction  Lytic Cycle: Use host machinery to make copies of virus Use host machinery to make copies of virus Death of host cell by rupturing it (lysis) Death of host cell by rupturing it (lysis) Virulent phages replicate by this method Virulent phages replicate by this method  Lysogenic Cycle: Phage DNA incorporated into host DNA and replicated along with it Phage DNA incorporated into host DNA and replicated along with it Phage DNA = prophage Phage DNA = prophage  Temperate Phage: uses both methods of replication

13. Lytic Cycle vs. Lysogenic Cycle

14. Animal viruses have a membranous envelope  Host membrane forms around exiting virus  Difficult for host immune system to detect virus

15. VIDEO: HOW DENGUE VIRUS ENTERS A CELL HOW DENGUE VIRUS ENTERS A CELLHOW DENGUE VIRUS ENTERS A CELL Watch this!

16. Retrovirus  RNA virus that uses reverse transcriptase (RNA  DNA)  Newly made viral DNA inserted into chromosome of host  Host transcribes viral DNA (= provirus) to make new virus parts  Example: HIV (Human Immunodeficiency Virus)

17. HIV = Retrovirus

18. HIV ◦ Infects white blood cells ◦ HIV+: provirus (DNA inserted) ◦ AIDS: active viral reproduction

19. VIDEO: HIV LIFE CYCLE HIV LIFE CYCLEHIV LIFE CYCLE Watch this!

20. Other Human Viruses  Herpes virus  Smallpox Herpes Simplex Virus 1 (HSV-1) Herpes Simplex Virus 2 (HSV-2) Eradicated in 1979 due to worldwide vaccination campaigns

21. Ebola Transmission: contact with contaminated blood or bodily fluids Transmission: contact with contaminated blood or bodily fluids Symptoms: fatigue, fever, severe headache, vomiting, diarrhea, rash, bleeding Symptoms: fatigue, fever, severe headache, vomiting, diarrhea, rash, bleeding ◦ May appear 2-21 days after exposure

22. Ebola Treatment: Treatment: ◦ Intravenous fluids, balance electrolytes ◦ Experimental: antiviral drugs, plasma transfusions from survivors, antibodies (Zmapp) ◦ No vaccine (yet) Statistics: Statistics: ◦ 2014 Ebola Outbreak (worldwide): 21,382 cases, 8474 deaths (*as of 1/19/15) ◦ Seasonal Influenza: estimated 36,000 deaths in U.S. each year (2015: mutated H3N2 strain)

23. 2014 Ebola Outbreak

24. Cumulative Ebola Cases

25. Vaccines  Weakened virus or part of pathogen that triggers immune system response

26. Emerging viruses = mutation of existing viruses

27. Viroids  Small, circular RNA molecules that infect plants  Cause errors in regulatory systems that control plant growth  eg. coconut palms in Philippines

28. Prions  Misfolded, infectious proteins that cause misfolding of normal proteins  eg. mad cow disease (BSE),Creutzfeldt-Jakob disease (humans), scrapie (sheep)

29. Diseases caused by prions  Prions act slowly – incubation period of at least 10 years before symptoms develop  Prions are virtually indestructible (cannot be denatured by heating)  No known cure for prion diseases