1. Viruses – Cellular Pirates
Enteric Adenovirus is an Icosahedral virus - common shape
Chicken Pox – contains an envelope – membrane taken from the host – contains host glycoprotein trick the host cell into taking in the virus
Adenovirus showing Varicella zoster virus
icosahedral shape causes chickenpox 1

2. Characteristics of Viruses
Obligate Intercellular Parasite
- Must reproduce(replicate) inside a host
Structure
- Nucleic Acid – DNA or RNA
- Protein coat – called a capsid
Envelope – some contain a layer of membrane taken
from a host cell
Mutate Rapidly
Host Specific can only infect one type of cell
Small – from 20nm to 250nm most are too small to be seen with a light microscope 2

3. Virus Structure
Helical virus – hollow tube of protein, icosahedron, phage 3

4. Bacteriophage Bacteriophages are viruses that infect bacteria
- they are responsible for transduction in bacteria 4

5. Viruses have two life cycles
Lytic Cycle-Viruses-immediately infect the host cell
Lysogenic Cycle - lay dormant in the cell 5

6. Lytic Cycle 6

7. Small Pox- Lytic Jenner developed first vaccine 1798
Small pox virus can only live in humans. Spread person to person generally through close contact with infected person. Symptoms appear 12 –14 days after exposure. 1st symptoms are fever, tiredness, severe back pain, stomach pain and vomiting. This last 2-3 days and at this time the person is highly contagious to others.Then over the next 5 days the bumps appear. Today we have a vaccine for small pox. We have 15.5 million doses available now. A contract has been made to produce 210 million does this year!! Today the risk of the disease is less than the risk from the vaccine so people do not get vaccinated. Vaccine can be helpful if you are exposed up to 4 days after exposure. 7

8. Lysogenic Cycle 8

9. Herpes Simplex 1/Lysogenic9

10. Shingles-Lysogenic/ Chicken pox virus (herpes varicella-zoster)
Shingles is caused by the chicken pox virus. It can develop in anyone who has had chicken pox. The chicken pox virus remains dormant or inactive (lysogenic cycle) in nerve root cells of the body. Shingles is the second outbreak of the chicken pox virus. Usually happens in older people (65) because of weakened immune system.Typical case of shingles lasts about a month. If you get it on your face you should see a physician because it can led to blindness. 10

11. Lytic and Lysogenic Cycles11

12. Retroviruses Contain RNA and not DNA
- to be able to take over a host cell, the retrovirus must be able to convert the RNA into DNA
- to accomplish the conversion, retroviruses insert an enzyme called Reverse Transcriptase into the host cell

13. Retroviruses

14. Vocabulary Obligate intercellular parasite Capsid Envelope
bacteriophage
Lytic Cycle
Lysogenic Cycle
Phage
prophage
Retrovirus
Reverse Transcriptase 14