1. Chapter 18 - Viruses

2. What is a virus? Made of two parts Capsid—Nucleic acid
Different shapes (477)

3. Viruses: composed of nucleic acids enclosed in a protein coat (Capsid)

4. Virus Transmission

5. Only infect certain things
Bacteriophage

6. Lytic Life Cycle

7. Viral Replication Cycles Lytic cycle
A virus invades a cell. Takes over the host cell’s genes to make new viruses.
This causes the cell to burst and more viruses are released.

8. Viruses that go through lytic cycle
Common cold
Flu
Measles
Chicken pox
Ebola
Smallpox
Polio

9. Lysogenic cycle
This is a replication cycle in which the DNA is integrated into the host cell’s chromosomes. Cells replicate with viral genes.
Each new cell has viral genes.
Virus can sit idle for many years before becoming active.
Example: hepatitis, HIV

10. Lysogenic Life Cycle

12. Viruses that go through the lysogenic cycle (Provirus) pg 481
Chicken pox
Herpes
Hepatitis

13. Symptoms of Provirus
Herpes simplex 1 – Cold sore; virus continues to live in body on nerve.
Stress could cause the activation of lytic cycle
Cold sores are not genital herpes

14. Chicken pox Genital Herpes
Cold sores
are different strains

15. Genital warts gone crazy!!!

16. HIV / AIDS Retrovirus—made of RNA (pg 481, Fig 18.5)
Infects white blood cells and destroys them
Lysogenic life cycle

17. Viruses are Specific
Viruses can usually attach to only a few kinds of cells.
Example: Polio viruses infect only intestinal and nerve cells.

18. Origin of Viruses Cells came first
Nucleic acids broke from an original host
First virus identified: Tobacco Mosaic Virus
This virus caused poor tobacco plant growth. Affected profit

19. Are Viruses Living? Not made of cells
Can reproduce, but only inside a host
Adapt / evolve
Do not utilize energy

20. Wash hands (hand sanitizer if you can’t wash), cover mouth, don’t touch face (nose, eyes, mouth)