1. Viruses – Cellular Pirates Adenovirus showing Varicella zoster virus icosahedral shape causes chickenpox

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

3. Virus Structure

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

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

6. Lytic Cycle

7. Small Pox- Lytic Jenner developed first vaccine 1798

8. Lysogenic Cycle

9. Herpes Simplex 1/Lysogenic

10. Shingles-Lysogenic/ Chicken pox virus (herpes varicella-zoster)

11. 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

12. Retroviruses

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