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Chapter 18 - Viruses

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  1. Chapter 18 - Viruses

  2. What is a virus? • Made of two parts • Capsid—Nucleic acid • Different shapes (477)

  3. Viruses: composed of nucleic acids enclosed in a protein coat (Capsid)

  4. Virus Transmission

  5. Only infect certain things • Bacteriophage

  6. Lytic Life Cycle

  7. Viral Replication CyclesLytic cycle • A virus invades a cell. Takes over the host cell’s genes to make new viruses. • This causes the cell to burst and more viruses are released.

  8. Viruses that go through lytic cycle • Common cold • Flu • Measles • Chicken pox • Ebola • Smallpox • Polio

  9. Lysogenic cycle • This is a replication cycle in which the DNA is integrated into the host cell’s chromosomes. Cells replicate with viral genes. • Each new cell has viral genes. • Virus can sit idle for many years before becoming active. Example: hepatitis, HIV

  10. Lysogenic Life Cycle

  11. Viruses that go through the lysogenic cycle (Provirus) pg 481 • Chicken pox • Herpes • Hepatitis

  12. Symptoms of Provirus • Herpes simplex 1 – Cold sore; virus continues to live in body on nerve. • Stress could cause the activation of lytic cycle • Cold sores are not genital herpes

  13. Chicken pox Genital Herpes Cold sores are different strains

  14. Genital warts gone crazy!!!

  15. HIV / AIDS • Retrovirus—made of RNA (pg 481, Fig 18.5) • Infects white blood cells and destroys them • Lysogenic life cycle

  16. Viruses are Specific • Viruses can usually attach to only a few kinds of cells. • Example: Polio viruses infect only intestinal and nerve cells.

  17. Origin of Viruses • Cells came first • Nucleic acids broke from an original host • First virus identified: Tobacco Mosaic Virus This virus caused poor tobacco plant growth. Affected profit

  18. Are Viruses Living? • Not made of cells • Can reproduce, but only inside a host • Adapt / evolve • Do not utilize energy

  19. Wash hands (hand sanitizer if you can’t wash), cover mouth, don’t touch face (nose, eyes, mouth)