2. CHAPTER 19 NOTES VIRUSES

3. CHARACTERISTICS OF VIRUSES Prokaryotic or Eukaryotic: Neither (no organelles or membranes) Unicellular or Multicellular: Neither (nucleic acid covered by a protein) Autotroph or Heterotroph: Neither (food is not metabolized for energy) Which Kingdom do they belong to? None

4. CHARACTERISTICS OF VIRUSES 2 MAIN PARTS OF A VIRUS: 1. PROTEIN COAT (CAPSID): PROTECTS THE NUCLEIC ACID CORE 2. CORE OF NUCLEIC ACID (CAN BE DNA OR RNA) An envelope is found in some viruses (usually those that infect animal cells). It is an additional protective coating. Many viruses have projections on their surface that allow it to enter a host cell.

5. EXAMPLE OF A BACTERIOPHAGE VIRAL DNA SHEATH TAIL FIBERS PROTEIN COAT (CAPSID)

6. 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. 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. See next page for drawings of the cycles.

9. LYTIC CYCLE

13. LYSOGENIC CYCLE

17. HOW ARE VIRUSES CLASSIFIED? VIRUSES CAN BE CLASSIFIED BY: – A. SHAPE – B. HOST – C. FUNCTION

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

19. Examples of Different Types of Human Viruses HIV

20. Examples of Different Types of Human Viruses Smallpox & Hanta virus

21. Examples of Different Types of Human Viruses Marburg & Lassa

22. Examples of Different Types of Human Viruses Ebola

23. THREE TYPES OF HOSTS A. PLANT Ex. Tobacco Mosaic Virus B. ANIMAL Ex. Rabies, Foot & Mouth Disease C. HUMAN Ex. Common cold, measles, chicken pox, mumps, HIV

24. 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.

25. HUMAN USES FOR VIRUSES 1. VACCINES 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 destroy that type of virus, if it enters the body again This helped to end epidemics of smallpox, polio and measles

26. HUMAN USES FOR VIRUSES 2. GENETIC ENGINEERING Viruses can help correct genetic defects by carrying desirable genes from one cell to another 3. AGRICULTURE Help control pests that destroy human food crops They eliminate harmful insects without creating pollution

27. Virus Video Clips http://ed.ted.com/lessons/how-pandemics- spread http://ed.ted.com/lessons/how-pandemics- spread http://www.youtube.com/watch?v=Rpj0emEGS hQ http://www.youtube.com/watch?v=Rpj0emEGS hQ http://www.youtube.com/watch?v=gf2bObJGFk g http://www.youtube.com/watch?v=gf2bObJGFk g