1. Viruses

2. Homework  Cell Analogy Project due Monday 10/5

3. Objectives  Know the two major differences between a virus and a cell  Know how a virus replicates itself

4. Viruses  How many viruses can the class name off the tops of our heads?

5. Viruses  How many viruses can the class name off the tops of our heads?  HIV, influenza, H1N1, rhinovirus, herpes, HPV, smallpox, polio, chickenpox, ebola, hanta, avian influenza, SARS, hepatitis, norovirus, dengue, Epstein-Barr, marburg, filoviruses  Major viruses you probably haven’t heard of include viruses infecting other animals (SIV, foot and mouth), many plant viruses (tobacco mosaic virus), bacteria viruses like T4 phage

6. Viruses  Is a virus another kind of bacteria?  How do they cause damage to the infected organism?

7. Definition  Virus = a microscopic infectious agent that replicates but is not truly alive* *By most scientists’ reckoning

8. Viruses  Viruses are not cells.  They have only two real parts, and only one of them can also be found in cells.

9. Viruses  They consist of a protein capsid (envelope or shell) that contains genetic material.  Often this genetic material is DNA, like a cell. Sometimes it’s closely- related RNA instead, in what are called retroviruses.

10. Viruses  This means cells have what parts that viruses don’t?  What does this mean that viruses cannot do for themselves?

11. Viruses  A virus can do one thing and one thing only: they force a cell (a host) to make more copies of the virus.

13. Viral Replication  http://videos.howstuffworks.com/hsw/80 61-viruses-how-viruses-work-video.htm http://videos.howstuffworks.com/hsw/80 61-viruses-how-viruses-work-video.htm  http://www.hhmi.org/biointeractive/medi a/viral_lifecycle-lg.mov http://www.hhmi.org/biointeractive/medi a/viral_lifecycle-lg.mov  http://student.ccbcmd.edu/courses/bio141 /lecguide/unit3/viruses/adlyt.html http://student.ccbcmd.edu/courses/bio141 /lecguide/unit3/viruses/adlyt.html  In spite of this, it’s not usually lysing cells that cause pain and symptoms, but it’s actually the body’s defense mechanisms that cause discomfort.

14. Checkpoint  How is a virus different from a cell?  How is viral replication different from how a cell can reproduce?

15. Viruses in History  Smallpox and the destruction of Native American civilizations  Mexico’s population: 18 million to 1.6 million in 100 years  American & Canadian Nations reduced to 5% of former population (20 million) in 200 years  Smallpox eradication in 20th century

16. Viruses in History  Influenza Pandemic of 1918  http://videos.howstuffworks. com/hsw/8063-viruses-the- influenza-pandemic-of- 1918-video.htm http://videos.howstuffworks. com/hsw/8063-viruses-the- influenza-pandemic-of- 1918-video.htm

17. Viruses in History  HIV pandemic  HIV mutated from SIV  The more closely related two species are, the easier it is for them to share viral illnesses  Discovered in the 1980s, 25 million dead since 1981  1/3 in Subsaharan Africa, ~6% children  Fast mutating, no cure or vaccine yet.  Clearly understood transmission & pathology  Many treatments & application of evolutionary principles mean it’s no longer “a death sentence” with medical assistance, but still a pandemic.

18. Viruses in History  Applications in Biotechnology  Knowing what you do about how a virus replicates, why do you think scientists look to viruses to help treat genetic disorders?

19. Unanswered Questions  Last remaining stores of smallpox in U.S. and Russia?  Herd immunity vs. individual freedoms - parents refuse vaccination for children?  Viruses used to modify genes for agriculture, medicine?