1. VIRUSES

2. What is a Virus? Made up of DNA or RNA surrounded by a protein coat Made up of DNA or RNA surrounded by a protein coat Cause disease and infection Cause disease and infection Not living (no growth, development or respiration) Not living (no growth, development or respiration) Need a host cell to replicate (make copies), Need a host cell to replicate (make copies),

4. Virus Structure Different shapes and sizes but all have: Different shapes and sizes but all have: 1. RNA or DNA in core 1. RNA or DNA in core 2. protein coat around nucleic acid called capsid 2. protein coat around nucleic acid called capsid 3. Some have envelope – acts like a disguise in host. 3. Some have envelope – acts like a disguise in host.

6. Many viruses are host specific! Many viruses are host specific! Ex. Small pox infects only humans Ex. Small pox infects only humans Other viruses infect many species. Other viruses infect many species. Ex. Flu infects humans and other animals (pigs, birds) Ex. Flu infects humans and other animals (pigs, birds)

7. How do viruses replicate? Lytic vs Lysogenic Cycles

10. Lytic Cycle 1. Attachment - virus attaches to host cell 1. Attachment - virus attaches to host cell 2. Entry - virus injects its DNA or RNA into host cell 2. Entry - virus injects its DNA or RNA into host cell 3. Replication – viral parts are made using genetic code of virus and raw materials of host 3. Replication – viral parts are made using genetic code of virus and raw materials of host 4. Assembly – virus particles are assembled 4. Assembly – virus particles are assembled 5. Lysis and release – host cell bursts releasing new virus particles 5. Lysis and release – host cell bursts releasing new virus particles Ex. Bacteriophage virus infecting bacteria host cell

11. Lytic Cycle

13. Lytic Virus Characteristics and Examples Infect host cell and start replicating immediately (cycle takes ~30 minutes and creates 200 new viruses!) Infect host cell and start replicating immediately (cycle takes ~30 minutes and creates 200 new viruses!) cause disease symptoms within days cause disease symptoms within days Small Pox, Measles, Polio, Cold virus, Seasonal Influenza Small Pox, Measles, Polio, Cold virus, Seasonal Influenza

14. Small pox

15. Measles

16. Polio

18. Lysogenic Cycle 1. Attachement 1. Attachement 2. Entry 2. Entry 3. Provirus formation – virus DNA is incorporated into host DNA 3. Provirus formation – virus DNA is incorporated into host DNA 4. Host Cell division – host cell copies all DNA including viral DNA, then divides 4. Host Cell division – host cell copies all DNA including viral DNA, then divides 5. Provirus activation – provirus removes itself from host DNA 5. Provirus activation – provirus removes itself from host DNA 6. Lytic cycle begins 6. Lytic cycle begins

19. Lysogenic Cycle

21. Lysogenic Virus Characteristics and Examples Provirus enters host cell and remains inactive usually months to years Provirus enters host cell and remains inactive usually months to years Examples: Examples: Hepatitis Hepatitis Herpes Herpes

22. Picture of hep b virus w/ large viral protein filiments secreted by infected cell Picture of hep b virus w/ large viral protein filiments secreted by infected cell

23. Herpes symplex 1 virus

24. Plant viruses Tobacco mosaic virus Tobacco mosaic virus RNA virus RNA virus First virus identified First virus identified

25. Tomato Plant Virus Tomato Plant Virus RNA virus RNA virus

27. Retro Viruses viruses with RNA viruses with RNA When injected into host cell, they must inject enzyme called reverse transcriptase to make DNA When injected into host cell, they must inject enzyme called reverse transcriptase to make DNA Ex. HIV Ex. HIV

28. Other Virus facts Some viruses are linked to cancer Some viruses are linked to cancer Ex. Hepatitis B – liver cancer Ex. Hepatitis B – liver cancer Ex. Human Papillomavirus (HPV) – cervical cancer Ex. Human Papillomavirus (HPV) – cervical cancer Prions – similar to virus, but only have protein (no nucleic acids) Prions – similar to virus, but only have protein (no nucleic acids) Ex. Mad Cow Disease caused by prion Ex. Mad Cow Disease caused by prion Viroids – similar to virus, but only have RNA Viroids – similar to virus, but only have RNA Cause many plant infections Cause many plant infections

29. Mad Cow Disease in Humans

30. Emerging viruses viruses that may have opportunity to reach epidemic proportions due to human encroachment eBola (left) – causes hemorrhagic fever eBola (left) – causes hemorrhagic fever Hanta virus (right) –causes respiratory failure Hanta virus (right) –causes respiratory failure Deer mouse (bottom) – carrier of hanta virus Deer mouse (bottom) – carrier of hanta virus

32. Ebola

33. Which came first? Viruses or cells

34. Scientists believe the host cells evolved first. Scientists believe the host cells evolved first. Viruses need host cells to replicate Viruses need host cells to replicate