1. Lesson 3 Viruses

2. Virus Tiny “organism” that is parasitic to cells Composed of two main parts: Protein outer shell called capsid Genetic material inside (DNA or RNA) Not classified as living Do not have cells Require cells to replicate Likely evolved after cells came into existence

3. Virus Cause some of the most common illnesses, ex: Common cold, the flu, cold sores, etc Cause some of the deadliest diseases, ex: Ebola, avian flu, AIDS

4. Virus Cannot be killed by antibiotics Antibiotics kill bacteria People can be protected against viruses with vaccines Ex. Flu shot

5. RNA or DNA? Viruses with RNA (higher mutation rate) Human immunodeficiency virus (HIV) Influenza viruses Rabies Measles, mumps, pneunomia, polio, common cold SARS Viruses with DNA (usually stable/constant, vaccines effective ) Chickenpox, cold sores, genital herpes Mononucleosis Hepatitis Respiratory infections, tumours

6. Virus Shapes 1.Helical (a spiral rod) 2.Polyhedral (many sides) 3.Complex (polyhedral capsid attached to a helical tail)

7. Virus reproduction Go through process called “Lytic Cycle”

8. Virus reproduction Go through process called “Lytic Cycle”

9. Virus reproduction Go through process called “Lytic Cycle”

10. Virus reproduction Go through process called “Lytic Cycle”

11. Virus reproduction Go through process called “Lytic Cycle”

12. Viruses are host cell specific Viruses usually infect only 1 type of host or even one cell type Some viruses can infect many species Ex. Rabies, swine flu

13. How are viruses spread? Vectors – carriers of viruses from one host to another May include: Insects (yellow fever, West Nile) Animals (rabies) Water (polio) Air (influenza, common cold, chicken pox) Humans (influenza, hepatitis, HIV)

14. Virus applications Studying molecular biology Genetically modify organisms Virotherapy: using viruses to treat diseases Kill bacteria Kill cancer Insecticide Biological warfare

15. Homework 1.What is a virus? 2.Are viruses alive? Why or why not? 3.Name 2 characteristics of viruses 4.What is the difference between a host and a parasite? 5.What are 3 different vectors for viruses? 6.Can a tobacco mosaic virus infect a human? Why or why not? 7.Describe the life cycle of a virus.