BIOL41 Lecture Exam2 -2

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daynuhmay
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183866
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BIOL41 Lecture Exam2 -2
Updated:
2012-11-15 14:29:37
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microbio
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BIOL41 Lecture Exam2 (2) Viruses,GrowthControl
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  1. 2 things all viruses have
    • 1) capsid
    • 2) genome
  2. What is a capsid made of?
    capsomeres
  3. nucleocapsid
    capsid + genome
  4. What do cells have that viruses don't?
    organelles
  5. What is a viral envelope made of?
    phospholipid bilayer obtained from previous host cell
  6. How big are viruses?
    • 10-400nm
    • 1/2 the size of bacterial cell
  7. 3 shapes viruses come in
    • 1) helical
    • 2) polyhedral
    • 3) complex
  8. What gives viruses their shape?
    way in which capsomeres bond together
  9. 2 phases of viral replication cycle
    • 1) extracellular/virion
    • 2) intracellular/replicating
  10. Extracellular replication cycle
    • just as a virion (particle itself)
    • not metabolizing
  11. Intracellular replication cycle
    • replicating DNA
    • typically no longer in virion shape (outside of capsid)
    • nucleic acid uncoated
    • has gained access to cell's metabolic machinery
  12. 4 types of viral genomes
    • 1) dsDNA
    • 2) ssDNA
    • 3) dsRNA
    • 4) ssRNA
  13. Most common type of viral genome
    • dsDNA for bacteriophages
    • ssRNA for plant viruses
  14. bacteriophage
    virus that infects bacteria
  15. bacteriophage replication
    • 1) attachment to bacterial cell
    • 2) entry/penetration into cell - tail penetrates cell membrane and phage DNA is released
    • 3) bacterial DNA degraded
    • 4) biosynthesis of viral DNA/phage proteins
    • 5) assembly/maturation of DNA packaged phage particles
    • 6) release of virions by lysis of bacterial cell
  16. 2 mechanisms used by ENVELOPED viruses to attach/enter the host cell
    • 1) receptor-mediated adsorption (host membrane protein R binds to viral glycoprotein )
    • 2) membrane fusion of envelope and cell membrane (capsid dropped inside) ex: HIV
  17. 3 mechanisms naked viruses use to attach/enter host cell
    • 1) receptor-mediated adsorption
    • 2) endocytosis
    • 3) direct penetration
  18. Once a virus enters a cell, what must it do?
    • 1) replicate genome
    • 2) make new viral components
  19. DNA animal virus replication
    • 1) enveloped DNA virus fuses with cell
    • 2) capsid shed in cytoplasm
    • 3) DNA enters nucleus
    • 4) cellular enzymes replicate genome into mRNA, capsomeres  made in ribosomes
    • 5) capsomeres enter nucleus where new virions assemble
    • 6) envelope acquired through nucleic membrane
  20. retrovirus
    • sense(+)-ssRNA virus (2 strands)
    • use DNA intermediary from +RNA transcribed by own reverse transcriptase as template for additional +RNA

    ex: HIV
  21. reverse transcriptase
    • uses RNA as template for DNA genome
    • does reverse reaction of normal transcription
  22. provirus
    virus genome that is integrated into the DNA of a host cell

    passively replicated along with the host genome and passed on to the original cell's offspring; all descendants of the infected cell will also bear proviruses in their genomes
  23. How do animal viruses exit host cells? 
    • 1) budding (enveloped viruses)
    • 2) exocytosis (naked)
    • 3) lysis/cell death (naked)
  24. cytopathic effect (CPE)
    viruses invade and damage/kill cells
  25. 7 mechanisms of CPEs
    • 1) DNA damage, translation/transcription halted
    • 2) lysosomes
    • 3) plasma membrane
    • 4) viral protein toxicity can disrupt cell mechanisms
    • 5) inclusion bodies form from buildup of viral protein
    • 6) chromosomal disruptions can lead to cells growing out of control
    • 7) malignant transformation
  26. lytic infection
    • viruses get in, replicate, cause damage, and get out
    • quick, dramatic effects
    • cells left dead
  27. persistent infection
    • reproduce at slower rate
    • host cells shed viruses slowly and steadily
    • host cell not quickly lysed
  28. latent infection
    • virus remains dormant in cells
    • undetected until it becomes active
    • CAN turn lytic
  29. oncogene
    • gene that has the potential to cause cancer
    • often involved in regulation of cell growth/differentiation
  30. cancer associated with EBV
    nasopharyngeal carcinoma
  31. cancer associated with HBV
    liver cancer
  32. cancer associated with HPV
    cervical cancer
  33. prion
    • clump of infection protein that causes change in protein structure
    • infectious forms build up in cytoplasm of neurons
    • normal and infectious forms
    • no nucleic acid
  34. diseases associated with prions
    • mad cow
    • Creutzfeld-Jacob disease
    • Kuru
    • spongiform encephalopathy
    • BSE

    lack of coordination, clumsy
  35. PrPc vs PrPsc
    • PrPc is "prion protein in cell" (normal form)
    • PrPsc is "prion protein in scrapie" (infectious, inverted form)

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