1. Viruses

2. Definition = Latin for POISON
NON – Living because
Do not grow
Do not reproduce on their own
Do not metabolize
Living Because
Evolve/Adapt
Mutate and recombine

3. Discovery of the Virus
Adolph Meyer (1833) a German Scientist studied the Tobacco Mosaic Virus.
Thought it was caused by a very small bacterium because it could not be viewed through the microscope.

4. Infection by tobacco mosaic virus (TMV)

5. VIRUSES: GENES IN PACKAGES
Viruses sit on the fence between life and nonlife
VIRION = a virus particle
Our body sees viruses as non living antigens and makes antibodies to fight them.

6. Viruses are parasites of cells.
A virus takes over its cellular metabolism (think cellular factory) and makes hundreds, if not thousands of copies.

7. Viruses are specific for the kinds of cells they infect. For example:
Influenza attacks only cells of the lungs.
Hepatitis C attacks only liver cells.
HIV attacks T4 white blood cells.

8. Examples of Different Types of Human Viruses
Influenza (Flu)

9. HIV

10. Herpes Virus

11. Measles

12. Ebola Virus

13. Polio

14. 2 MAIN PARTS OF A VIRUS:
1. Protein coat (capsid): Protects the nucleic acid core
2. Nucleic acid core – can be DNA or RNA
An envelope is found in some viruses (usually those that infect animal cells). It is an additional protective coating.

15. Membranous
envelope
RNA
Protein
coat
Protein
spike

18. EXAMPLE OF A BACTERIOPHAGE (attacks bacteria)
PROTEIN COAT (CAPSID)
VIRAL DNA
SHEATH
TAIL FIBERS

19. Compare the size of a Eukaryotic cell, Bacterial Cell and a Virus

20. Viruses come in many shapes and sizes
Measured in nanometers (nm)
There are 109 nm in a meter
(1 nm = 10-9 m)
Cannot be seen with a light microscope

22. HOW ARE VIRUSES CLASSIFIED?
TYPE OF NUCLEIC ACID (DNA or RNA)
SHAPE
B. HOST
C. FUNCTION

23. Bacteriophages Bacteriophage is a virus that attacks bacteria
Injects its DNA and takes over the bacteria cell.
Phage: means to eat or destroy

24. 0.5 m

25. Head
Tail
Tail fiber
DNA of virus
Bacterial
cell

26. HOW DO VIRUSES MULTIPLY?
Viruses perform replication in other cells called hosts.
The two replication cycles that viruses go through are the LYTIC and the LYSOGENIC cycles.

27. The two cycles differ because in the lytic cycle a virus immediately replicates after entering the cell and in the lysogenic cycle the viral DNA replicates itself in a way that doesn’t kill the host cell immediately.

30. LYTIC CYCLE

34. LYSOGENIC CYCLE

38. TREATMENT OF VIRAL DISEASES
Viral diseases cannot be cured by antibiotics.
Generally with viral infections you are limited to relieving symptoms while your immune system battles the virus.

39. Prevention of Viral Infections – VACINES
When you inject a person with a harmless (weakened or dead) form of a virus
This stimulates the immune system to produce cells and proteins that will recognize and destroy that type of virus, if it enters the body again

40. This helped to end epidemics of smallpox, polio and measles

41. HUMAN USES FOR VIRUSES GENETIC ENGINEERING
Viruses can help correct genetic defects by carrying desirable genes from one cell to another

42. AGRICULTURE
Help control pests that destroy human food crops
They eliminate harmful insects without creating pollution