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Viruses

Viruses. What is the structure and function of viruses?. How Germs Spread. What is a virus?. Tiny, nonliving particles Need a host cell to reproduce Named based on disease or tissue – NO Latin names Ex. bacteriophage, rabies virus, adenovirus. Viral Structure.

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Viruses

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  1. Viruses What is the structure and function of viruses? How Germs Spread

  2. What is a virus? • Tiny, nonliving particles • Need a host cell to reproduce • Named based on disease or tissue – NO Latin names • Ex. bacteriophage, rabies virus, adenovirus

  3. Viral Structure • Core - nucleic acid DNA/RNA • Protein coat - capsid • Some larger viruses have an outer viral envelope

  4. Capsid Nucleic acid Envelope

  5. Viral Shapes • Importance - recognize specific host cell • Cell-type specific or species specific • Ex: polio virus – human nerve cells Ebola virus

  6. Common virus shapes • Polyhedral • Cylindrical • Spherical • Polyhedral w/a tail

  7. Attachment and Entry

  8. Lytic Cycle • Attachment • Entry • Replication • Assembly • Lysis and Release • Ex. flu or Influenza

  9. Bacteriophage Bacterial DNA Nucleic acid Bacterial host cell B. Entry A. Attachment The bacteriophage injects its nucleic acid into the bacterial cell. E. Lysis and Release The host cell breaks open and releases new virus particles. C. Replication D. Assembly The host’s metabolic machinery makes viral nucleic acid and proteins. New virus particles are assembled.

  10. Lytic Cycle Animation

  11. Lysogenic Cycle • Attachment & Entry • Provirus forms • Cell Division • Provirus leaves host DNA – why? • Lytic cycle

  12. Lysogenic Cycle Animation

  13. Lytic and Lysogenic cycles

  14. B. Provirus Formation A. Attachment and Entry Provirus Although the provirus is inactive, it replicates along with the host cell’s chromosome. C. Cell Division Bacterial host chromosome A lysogenic virus injects its nucleic acid into a bacterium. The viral nucleic acid is called a provirus when it becomes part of the host’s chromosome. LYSOGENIC CYCLE LYTIC CYCLE The provirus leaves the chromosome. The cell breaks open releasing viruses. Viral nucleic acid and proteins are made.

  15. HIV virus AIDS • Lysogeniccycle • Retrovirus – RNADNA • HIV bud off w/out killing white blood cells

  16. Other Viral Diseases • Common Colds & Influenza • Smallpox • Human papillomavirus  warts • Herpes simplex  Cold sores fever blisters

  17. Defenses & Treatments • Phagocytes white blood cells • Antibodies • Vaccine –before exposure • Antibiotics do NOT work • Treat symptoms • Wash hands – remember the video clip

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