2. What is a virus?  small infectious agent that can replicate only inside the cells of other organisms. Viruses are too small to be seen directly with a light microscope.

3. What can all viruses do?  REPRODUCE!!!  They can not reproduce on their own  Viruses require a HOST cell to infect and reproduce HOST= another organisms cell

4. What are viruses named after?  Named after the disease they cause  Ex:  Influenza virus causes the influenza or the flu  Poliomyelitis causes polio  Chicken pox virus causes chicken pox

5. What is a virus that infects a bacterium called?  Called a  bacteriophage

6. Viral Structure  2 Major Parts  Inner Core  genetic info.  Viruses have either RNA or DNA as genetic material  Outer Core  capsid head

7. Viral Replication Cycle  2 Types of Cycles  LYSOGENIC and LYTIC  Lytic Replication: virus injects genetic info inside host cell, replicates, and lyses (burst and kills) the host cell as viruses leave the cell particle. ATTACH  INJECT  SYNTHESIZE  LYSE  Lysogenic Replication: viral genetic info becomes incorporated with host cell. Viral genetic info is now replicated every time host cell makes new cell

8. LYTIC CYCLE

9. LYSOGENIC CYCLE

10. Viruses Website  http://leavingbio.net/VIRUSES%20WEBPAGE.ht m http://leavingbio.net/VIRUSES%20WEBPAGE.ht m  http://www.courses.fas.harvard.edu/~biotext/ani mations/lysogeny.html http://www.courses.fas.harvard.edu/~biotext/ani mations/lysogeny.html  http://www.courses.fas.harvard.edu/~biotext/ani mations/lyticcycle.html http://www.courses.fas.harvard.edu/~biotext/ani mations/lyticcycle.html

11. PROVIRUS  Viruses that use the lysogenic cycle  They incorporate themselves into the host DNA  Can replicate without lyses of the cell  Retroviruses are proviruses  HIV is an example a provirus

12. Why are retroviruses so different  Takes its genetic information (RNA) and tricks the host manufacture its viral DNA.  Host then replicates its own as well as the retrovirus DNA  Oncogenic viruses will convert normal cells into tumor cells (Oncoviruses, Lentiviruses)

13. First Virus Identified  Tobacco mosaic virus  Infected tobacco and other plants  Discovered in 1892 by Dmirti Iwanowsk

14. Where do scientists suggest that viruses come from?  No clear answer  Some suggest that they came from parasites, others say that they were bits of genetic info that separated from a cell

15. Are all viruses bad?  No!!!  Viruses are being used for gene therapy. Take the bad genetic info out of the virus and replace it with good genes and inject the virus into people that have defective genes.  Vaccinations- weaken or dead viruses are injected into you to promote immunity

16. Diseases that are caused by viruses?  Flu  H1N1  Chicken Pox  Measles  HIV  Rabies  Small Pox  Ebola  LOTS MORE!!!!

17. The HIV Virus