1. Viruses
2.3

2. I. What are viruses?
Virus- A strand of hereditary material (DNA) surrounded by a protein coating.
1. Viruses are NOT alive!!!
2. Too small to be seen with a compound microscope

3. I. What are viruses?
B. Examples
1. Cold sores
2. Measles
3. Chicken Pox
4. Colds
5. Flu
6. AIDS

4. II. How Do Viruses Work
Viruses CANNOT survive without a host cell.
1. They use the cell to carry out the 5 life characteristics

5. II. How Do Viruses Work
B. Viruses can be active or latent.
1. Active viruses cause the host cells to make new viruses
a. The virus attaches to the host cell

6. II. How Do Viruses Work
b. The virus’ heredity material (DNA) enters the cell.
c. The heredity material causes the cell to make new viruses within the cell
d. The cell bursts and releases new viruses and the cell is destroyed

7. II. How Do Viruses Work
2. Latent viruses enter the cell, but do not become active right away.
3. It takes certain environmental conditions to activate the virus to start reproducing.
a. Cold Sores

8. III. Fighting Viruses Viruses can be PREVENTED by taking a vaccine
1. Smallpox was the first vaccine
a. Discovered by Edward Jenner
b. Injected small amount of cowpox virus which caused the body to prevent smallpox

9. III. Fighting Viruses
B. Viruses CANNOT be TREATED!!!
1. Your body must produce interpherons that protect the uninfected cells in order to stop the virus

10. III. Fighting Viruses
C. Viruses can be good!!!
1. Gene therapy- Scientists use viruses to insert “good DNA” into patients with “bad DNA” to make them better.

11. RECAP
-What is a virus?
-Why do viruses need a host cell?
-How do viruses take over the cell?
-What is the difference between a latent virus and an active virus?

12. RECAP
-How are viruses prevented?
-How are viruses treated?
-How can viruses be used for good?