1. Viruses The latin word for poison!!!

2. A Virus  Nonliving particle cosisting of a core of hereditary material surrounded by a protein coat.  Does not grow  Does not respond  Does not eat  Only reproduces  Can reproduce only inside a living cell (host cell)

3. Viruses  Some can be made into crystals and stored in a jar for years.  If opened, the virus can enter an organism (host), quickly reproduce, and cause new infections.  Causes damage to the organism

4. Classifying Viruses  Viruses come in a variety of shapes due to their protein covering.  They are responsible for many diseases.  They are classified by shape, the kind of hereditary material they have, the kind of organisms they infect, and their method of reproduction.

5. Naming Viruses  Viruses are often named after the disease they cause.  Ex: polio virus……causes polio disease  Also named after the organ or tissue they infect.  Ex: adenovirus…infects the adenoid tissues.

6. The T4 Virus  Also called a bacteriophage  Type of virus that infects bacteria.  Many sided head attached to a tail.  Injects its hereditary material into the cell through the tail, much like a hypodermic needle.

7. T4 Bacteriophage

8. What do viruses do?  Once inside a host cell, a virus can do 1 of 2 things.  1. Be active (Lytic)  2. Be latent: or be an inactive part of the cell for a while. (Lysogenic)

9. The Active Phase (overview)

10. The Active Virus (Step 1) Attach: a specific virus attaches to the surface of a specific bacterial cell.

11. The Active Virus (Step 2) Invade: Hereditary material of the virus injects itself into the bacterial cell.

12. The Active Virus (step 3) Copy: Viral heredity material takes control of the bacterial cell and the cell begins to make new virus particles.

13. The Active Virus (step 4) Release: Cell bursts open and hundreds of new virus particles are released. New particles go on to infect other cells.

14. The Latent Virus  The latent virus enters the cell and becomes part of the cells hereditary material without immediately destroying the cell or making new viruses.  May “hide” inside cells for many years.  May become active at any time.

15. The Latent Virus (overview)

16. Latent Virus (Step 1) Specific virus attaches to the surface of a specific bacterial cell. Hereditary mateial of the virus injects itself into the cell.

17. Latent Virus (Step 2) Virus becomes part of the bacterial cell’s chromosomes.

18. Latent Virus (Step 3) Bacterial cell divides.

19. Latent Virus (Step 4) Virus leaves chromosome and becomes active.

20. Latent Virus (Step 5) New viruses are made.

21. Latent Virus (Step 6) Bacterial cell breaks open and releases the viruses destroying the host bacterial cell.

22. Latent Virus Example  Cold Sore:  From latent phase to the active phase  Virus enters the cell is remains latent.  Stress, too much sun or cold makes the virus become active.  Sores become abundant.  Sores disappear; virus becomes latent again.  Still present, just not active.

23. Viral Diseases  May cause disease in plants, animals, fungi, bacteria, and protists.  No antibiotic medications to cure viruses.  Can be prevented by vaccines.  Vaccines made from damaged virus that can no longer cause disease.

24. Vaccine Example  Edward Jenner  Developed vaccine in 1796 for smallpox.  Smallpox was a greatly feared disease.  Prepared the vaccine from using some of the samples taken from the sores of the milkmaids that had cowpox.  Injected the material into healthy people.  Protected them against the smallpox virus.

25. The End