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Viruses

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Viruses

  1. 1. microbiology
  2. 2. Viruses <ul><li>Nucleic acid within a protein coat </li></ul><ul><li>Jenner – smallpox vaccine </li></ul><ul><li>Stanley – first virus </li></ul><ul><li>Not visible under light microscope </li></ul><ul><li>Non-living </li></ul><ul><ul><li>No metabolism </li></ul></ul><ul><ul><li>Cannot replicate </li></ul></ul><ul><ul><li>without a host </li></ul></ul><ul><ul><li>No scientific name, </li></ul></ul><ul><ul><li>instead family names </li></ul></ul>Influenza virus
  3. 3. Bacteriophages <ul><li>Viruses that infect bacteria </li></ul>Capsid protein DNA or RNA Tail Tail fibers
  4. 4. Structure of a Virus <ul><li>Shape varies – helix, bullet, round </li></ul><ul><li>Nucleic acid – either RNA or DNA </li></ul><ul><li>Outer protein capsid </li></ul><ul><li>Optional features for protection </li></ul><ul><ul><li>Envelope, spikes, slime layers </li></ul></ul>
  5. 5. Attaching to Cells <ul><li>Prior to replication, virus must enter cell </li></ul><ul><li>Protein on virus interlock with surface markers on cells </li></ul><ul><li>Each virus has specific cell to “dock” with </li></ul><ul><li>EX: polio virus attaches to nerve cells </li></ul>
  6. 6. Viral Replication Cycles <ul><li>Lytic </li></ul><ul><ul><li>Virus attaches to cell </li></ul></ul><ul><ul><li>Inserts DNA </li></ul></ul><ul><ul><li>Replication of viral parts </li></ul></ul><ul><ul><li>Assembly of new viruses </li></ul></ul><ul><li>Lysogenic </li></ul><ul><ul><li>Virus attaches to cell </li></ul></ul><ul><ul><li>Inserts DNA </li></ul></ul><ul><ul><li>DNA integrates into host DNA </li></ul></ul><ul><ul><li>Cell replicates normally with viral DNA altering protein synthesis </li></ul></ul><ul><ul><li>Proteins can create new viruses or not (latency) </li></ul></ul>
  7. 10. <ul><li>Inhibit protein synthesis of host </li></ul><ul><li>Open lysosomes </li></ul><ul><li>Bind membranes together </li></ul><ul><li>Create a toxic level of proteins </li></ul>How Viruses Damage Cells The human body protects itself from viruses using antibodies and fever. Viruses prefer body temperature.
  8. 11. Which of these diseases is likely to be caused by a lytic virus? Characteristics of some Viral Diseases Disease Symptoms Incubation Measles Rash, Fever 9-11 days Shingles Pain, itching on skin Years Warts Bumpy area on skin Months Influenza Body aches, fever, runny nose 1-4 days HIV fatigue, weight loss, fever 2-5 years

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