Viruses and prions

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Author:
kimiko
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278542
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Viruses and prions
Updated:
2014-07-09 23:27:18
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m122
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m122
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  1. what are viruses?
    protein and nucleic acid
  2. what are viroids?
    • only RNA
    • (circular ss RNA)
  3. what are satellites?
    • DNA or RNA only
    • do not encode their own vapid proteins
    • require a helper virus to replicate
    • encode one or more gene products
  4. what are Prions?
    proteins only
  5. what are the steps for disease production by prions
    • 1.abnormal prions interacts with normal protein
    • 2.normal protein is converted into the abnormal protein
    • 3. continued conversion of normal proteins until there is no more normal proteins
  6. what is viruses role in evolution?
    transfer genes between bacteria/ other organisms
  7. what are the general properties of irons?
    • consists of >1 molecule of DNA or RNA enclosed in a coat of protein
    • may have additional layers
    • cannot reproduce independent of living cells
  8. what is the virion size range?
    10 to 400 nm
  9. what is a capsid?
    • large macromolecular structures which serve as protein coat for the virus
    • It protects the viral genetic material and aids in its transfer between host cells
  10. what are the protein subunits of capsids?
    protomers
  11. what are the different shapes of capsids?
    • helical - hollow tubes with protein walls
    • icosahedral - regular polyhedron with 20 equilateral faces and 12 vertices
    • complex
  12. what is the outer flexible membranous layer in a virus called?
    envelope
  13. what are the function of viral envelope proteins?
    • viral attachment to host cell
    • identification of virus
    • enzymatic activity
    • may play a role in nucleic acid replication
  14. where are most virion enzymes located?
    within the capsid
  15. what are the steps for viral multiplication?
    • attachment to host cell
    • entry
    • uncoating of genome
    • synthesis
    • assembly
    • release
  16. what are the 3 methods used for uncoating of the genome?
    • fusion of the viral envelope with host membrane; nucleocapsid enters
    • endocytosis in vesicle; endosome aids in viral uncoating
    • injection of nucleic acid
  17. what must a RNA viruses carry in/synthesize to complete synthesis?
    proteins
  18. how are proteins assembled for viral multiplication?
    • some are assembled in the nucleus
    • some are assembled in the cytoplasm
  19. how are non enveloped viruses released from the cell?
    nonenveloped viruses lyse the host cell by attacking the peptidoglycan membrane
  20. how are enveloped viruses released from the cell?
    enveloped viruses use budding to merge with the host cell membrane and then are exocytosed
  21. what are the 2 reproductive options for temperate phages?
    • 1. reproduce lytically as virulent phages do
    • 2. remain within host cell without destroying it
  22. what is a prophage?
    phage that integrates their genome into the host genome
  23. what is a lysogenic relationship?
    virus does not replicate in bacteria with genes integrated into the genome
  24. what are the 2 advantages to lysogeny for a virus?
    • phage remains viable but may not replicate
    • multiplicity of infection ensures survival of host cell
  25. why does temperate phage chafes the phenotype of its host
    • bacteria become immune to superinfection
    • phage may express pathogenic toxin or enzyme
  26. when does a cell undergo induction?
    induction occurs when conditions in the cell cause the prophage to initiate synthesis of new phage particles
  27. what is neoplasia?
    abnormal new cell growth and reproduction due to loss of regulation
  28. what is anaplasia?
    reversion to a more primitive or less differentiated state
  29. what is metastasis?
    spread of cancerous cells throughout the body
  30. what are the possible mechanisms by which viruses causes cancer?
    • viral proteins bind host cell tumor suppressor proteins
    • carry oncogene into cell and insert it into host genome
    • altered cell regulation
    • insertion of promoter or enhancer next to cellular oncogene
  31. what are cytopathic effects (CPE)
    degenerative changes or abnormalities in host cells/ tissues because of viral infection
  32. what are plaque assays used for?
    to visualize the presence of a virus
  33. what are the 2 types of plaque assays?
    • cell (tissue) cultures - used for eukaryotes
    • bacteria cultures - used for bacteriophages
  34. what are the units used to express concentration of infectious units?
    • plaque-forming units (PFU)
    • PFU/ml = number of plaquest/sample dilution
  35. do prion disease have a treatment?
    no
  36. what must be present fro neural degeneration to occur?
    PrPc prion must be present for neural degeneration to occur

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