Micro ch 4

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Micro ch 4
2012-05-02 18:18:06

Micro Ch 4
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  1. Who postulated that rabies was caused by a virus?
    Louis Pasteur
  2. Key developments in virology are
    • Electron Microscope
    • Cultivation Techniques
  3. _____ viruses have been id and _____ are estimated to exist
    • 1500
    • 400,000
  4. List the 5 properties that distinguish viruses from living cells
    • They possess EITHER DNA or RNA (not both)
    • Unable to replicate on their own
    • They do not divide by binary fission, mitosis or meiosis
    • The do not have metabolism (enery production)
    • They depend on the ribsomes,enzymes, and metabolites of the host cell for nucleic acid production
  5. All viruses have _____
  6. Describe capsids
    Protein coats that enclose and protect their nucleic acid when outside the host cell
  7. Capsid + Nucleic acid =
  8. Each capsid is constructed from identical subunits called ____, which are made of _____
    • Capsomers
    • Protein
  9. Three structural types of capsids.
    • Helical-
    • Icosachedral-
    • Complex Viruses-
  10. Describe Helical
    Helical-continuous helix of capsomers froming cylindrical nucleocapsid
  11. Describe Icosahedral
    Icosachedral-20 sided with 12 corners
  12. Describe Complex
    • Atypical
    • Lack a typical capsid
    • Covered by dense layer of lipoproteins
  13. Some bacteriophages have a
    polyhedral nucleocapsid along with a helical tain and attachment fibers
  14. Describe Viral Envelope
    • Makes virus hard to get rid of
    • Mostly animal viruses
    • Flexible membrade that is similar to hosts membrane
    • Aquired when virus leaves host cell
    • Helps virus bind to cell surface
    • Assists penetration of the viral DNA or RNA
  15. Some viruses have finctional projections on the outside of the envelope called _____
  16. Spikes contain ____
    enzymes that are essential for attachment of virus to host cell
  17. 4 nucleic acid types of viruses
    • Double DNA
    • Single RNA
    • Single DNA
    • Double RNA
  18. Which genome type causes infection faster
    Single RNA
  19. Most viral genomes are which types?
    Double DNA and Single RNA
  20. Most viral genomes are circular molecules, but some are _____
  21. Define host range
    What organisms the virus can infect-based on capsid structure
  22. Define tissue tropism
    • tissue specifity-spectrum of cells a virus can infect
    • Hep B-liver cells
    • Poliovirus-intestinal and nerve cells
    • Rabies-various cells of many mammals
  23. Pneomotropic
    respiratory system infected
  24. Dermotrophic
    Skin infected
  25. Viserotrophic
    Organs infected
  26. Neurotrophic
    CNS infected
  27. The steps in mult of animal viruses are :
    • Attatchment/absorption
    • Penetration
    • Uncoating
    • Biosynthesis
    • Assembly
    • Release
  28. Describe attatchment/absorption
    binding of virus to specific molecule on host cell
  29. Describe penetration
    genome enters host cell
  30. Describe uncoating
    the viral nucleic acid is released from the capsid
  31. Describe Biosynthesis
    Viral components are produced
  32. Describe assembly
    new viral particles are constructed
  33. Release
    Animal viruses escape from their host cells by lysis or budding
  34. Difference between lysis and budding
    • Lysis-released with no envelope
    • Budding-viruses become enveloped
  35. Define latent virus infections
    • Viral inf in which the virus is able to hide from a hosts immune system by entering the cells and remaining dormant
    • ex. herpes
  36. Viruses are _____ ______ _____, they require appropriate cells to replicate
    • Obligate Intracellular Parasite
    • Makes them difficult to cultivate and id
  37. Cultivating methods
    • Bird embyos-virus injected through egg shell
    • Live animal inoculation
    • Cell/tissue cultures
  38. In cell cultures cells grop in sheets called ______ that support viral replication and permid observation for ______ effect
    • monolayers
  39. Define cytopathic effect
    • Virus-induced damaged to cells
    • Change in shape and size
    • Fusion of cells or cell lysis
    • Alter DNA-transformation-cancer cells
  40. List 4 examples of cytopathic effects
    • Negri bodies
    • Lipschutz bodies
    • Downey cells
    • Koplik spots
  41. Antiviral agents
    Drugs that are used to treat viral infections
  42. Antiviral agents interfere with _____ and _____ by disrupting critical phases in viral mult or inhibiting synthesis of viral DNA, RNA or proteins
    • virus specific enzymes
    • virus production
  43. Viral ____ offer the best protection against infection
  44. ____ and _____ agents can inactivate viruses
    • Physical
    • Chemical
  45. Viruses are responsible for ___ of human cancers
  46. HIV
    enveloped single stranded RNA virus
  47. Viroids
    • Short naked fragments of single stranded RNA
    • interfere with plant metabolism

    Ex: Potato spindle tuber, citrus exocortis
  48. Prions
    • Small infectious proteins that cause fatal neurologic diseases in animals
    • Most resistant to disinfectants
    • Idiopathic

    EX: mad cow disease