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Characterizing and Classifying Viruses, Viroids, and Prions

Characterizing and Classifying Viruses, Viroids, and Prions. Chapter 13. Comparing the size of a virus, a bacterium, and a eukaryotic cell. General Features of Viruses #1. Obligate Intracellular Parasites Very small (ultramicroscopic) Non-cellular Not Alive Protein Coat …Capsid

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Characterizing and Classifying Viruses, Viroids, and Prions

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  1. Characterizing and Classifying Viruses, Viroids, and Prions Chapter 13

  2. Comparing the size of a virus, a bacterium, and a eukaryotic cell

  3. General Features of Viruses #1 • Obligate Intracellular Parasites • Very small (ultramicroscopic) • Non-cellular • Not Alive • Protein Coat …Capsid • Envelopes (some viruses..not all)

  4. Viral structure

  5. General Features of Viruses #2 • Utilization of Host Cell Machinery • Host Range • Genome • DNA or RNA but NOT both • Single stranded or double stranded • Enzymes (Polymerases) (some viruses…not all)

  6. Emerging viral diseases Play Movie

  7. Virus Replication (Video clip-part1)(5 Basic Steps for all viruses) • Adsorption • Penetration • Replication • Maturation • Release

  8. The lytic cycle of phage T4

  9. The lysogenic and lytic reproductive cycles of phage , a temperate phage

  10. Lysogenic cycle video clip-part 2 • Lysogeny • Prophage • Temperate virus • Lysogenic conversion • Corynebacterium diptheriae

  11. The reproductive cycle of an enveloped virus • Attachment (adsorption) • Entry and Uncoating • Viral replication and protein synthesis • Assembly (maturation) • Release

  12. Entry and Uncoating of Animal Viruses Figure 13.12a-b

  13. Entry and Uncoatingof Animal Viruses Figure 13.12c

  14. Release of Enveloped Viruses by Budding Figure 13.13

  15. HIV, a retrovirus

  16. HIV reproduction Play movie

  17. Consequences of Viral Infection

  18. Cancer Some viruses are oncogenic • Protooncogenes • Oncogenes

  19. All forms of life have viruses that infect them Plant viruses

  20. Viroids • Short pieces of “naked” RNA • No Protein coat • Only known to infect plants • Cadang Cadang disease

  21. Prions • Infectious proteins • No nucleic acid involved • Cause degenerative brain diseases • Scrapie in sheep • Mad Cow Disease • Creutzfeldt-Jakob Disease • CWD Chronic Wasting Disease in deer/elk

  22. A hypothesis to explain how prions propagate

  23. Chronic Wasting Disease • Chronic Wasting Disease (CWD) is a transmissible neurological disease of deer and elk producing lesions in brains of infected animals. It is characterized by loss of body condition, behavioral abnormalities and death. CWD is classified as a transmissible spongiform encephalopathy (TSE), and is similar to mad cow disease and scrapie.

  24. Prion: CWD • Chronic Wasting Disease Chronic Wasting Disease Among Free-Ranging Cervids by County,United States, January 2007

  25. CWD in Iowa???...Not Yet! • Each season about 4,000 deer are tested…none positive • Since 2002 over 20,000 deer tested without a positive

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