Viruses: VI & VII Evolution of Viruses; Viroids and Prions

  1. a.      Viruses biologically __, unable to __ or __; but has genetic program written in __
    b.      Origin
                                                                  i.      Infect every form of life; depend on cells for own __not descendants of __forms of life but evolved after the first cells appeared
    • inert
    • replicate genes
    • regenerate ATP
    • universal language
    • propagationà
    • precellular
  2. a.      Hypothesis
    •                                                               i.      Viruses originated from naked bits of cellular nucleic acids that moved from one cell to another
    • 1.      Evolution of genes coding for capsid proteins facilitated infection of uninjured cells
  3. Plasmids
    • a.      : small, circular DNA molecules found in bacteria and in yeasts                                                                                                                                       i.      Exist apart from cell’s genome, replicate independently, and transferred from cell
  4. Transposons
    a.      DNA segments that can move from one location to another within a cell’s genome
  5. 3. Viruses, plasmids, and transposons are __
    mobile genetic elements
  6. a.      Viruses can have more in common with __ than __
                                                                  i.      Still, some have similarities
    1.      Genetic similarities reflect __ and persistence of groups of viral genes
    • genome of host than fellow virus
    • natural selection
  7. a.      __: largest virus yet discovered
                                                                  i.      __-stranded __virus with an __capsid that is 400 nm in diameter
    1.      Genome codes for products thought to be hallmarks of cell genomes
    a.      __(4)__
    • Mimivirus
    • Double
    • DNA
    • icosahedral
    • Proteins of translation, DNA repair, protein folding, polysaccharide synthesis
  8.                                                               i.      Proposals of mimivirus:
    • Evolved before first cells and exploited them
    • 2.      Virus evolved more recently than cells and efficient at taking genes from hosts
  9. a.      Viroids?
    Circular RNA molecules that infect plants
  10. Viroids do not __ but can __ in host plant cell, using host cell enzymes.
    Cause errors in __ that control __; the typical signs are __ and __.
    Single molecule can be an __ that spreads a disease.
    • encode proteins
    • replicate
    • regulatory systems
    • plant growth
    • stunted growth
    • abnormal development
    • infectious agent
  11. Prions
    •                                                               i.      Infectious protein which cause a number of degenerative brain diseases in animal species
    • 1.      Scrapie= sheep
    • 2.      Mad cow disease
  12. Means of Prion transmittance
  13. Alarming characteristics of prions
    • 1.      Act very slowly, with an incubation period of at least ten years before symptoms develop
    • a.      Lengthy incubation period prevents sources of infection from being identified until long after the first cases appear, allowing more infections to occur
    • 2.      Prions virtually indestructible
    • a.      Not destroyed or deactivated by heating to normal cooking temperatures
  14. Cure for prions?
  15.                                                               i.      Misfolded form of a protein normally present in __ cells
    1.      When prion gets into cell containing normal form of protein, the prion does what

    2.      Several prions then aggregate into a complex that can __
    • brain
    • somehow converts normal protein molecules to misfolded prion versions
    • convert other normal proteins to prions, which join the chain
  16.                                                               i.      Prion aggregation interferes with normal cellular functions and causes __symptoms
Card Set
Viruses: VI & VII Evolution of Viruses; Viroids and Prions