Bio Final Prep - Viruses

  1. Viruses are small infectious particles consisting of:
    • -Nucleic acid
    • -A protein coat
    • -(in some) a membranous envelope
  2. Viral genomes may consist of
    Double or single stranded DNA or RNA
  3. A capsid is
    • the protein shell that encloses the viral genome
    • -it's built of subunits called capsomeres
  4. Viral envelopes are derived from the host cell's membrane and surround
    the capsids of viruses
  5. What are the two reproduction mechanisms of phages?
    The lytic and lysogenic cycles
  6. The lytic cycle causes what?
    • Death of the host cell.
    • A phage that only undergoes the lytic cycle is called a virulent phage
  7. 5 stages of the lytic cycle?
    • Attachment
    • Entry of phage DNA, degredation of host DNA
    • Synthesis of viral genomes and proteins
    • Assembly
    • Release
  8. The lysogenic cycle replicates the phage and...
    does not destroy the cell
  9. Prophage is
    when viral DNA is incorporated into the host's chromosome during the lysogenic cycle
  10. Describe the process of the Lysogenic cycle
    • Phage injects the DNA into the cell
    • Prophage
    • The bacterium reproduces, copying the prophage
    • Cell divison produces more - daughter cells with prophase
  11. Temperate phages are...?
    Phages that use both the lytic and lysogenic cycles
  12. Two key variables used to classify viruses that infect animals?
    • 1) DNA or RNA?
    • 2) Single or double stranded
  13. Two possible candidates for viral genome sources?
    • Plasmids - circular DNA in bacteria and yests
    • Transposons - small mobile DNA segments
  14. Viroids are circular RNA molecules that infect...
    plants, and disrupt their growth
  15. Prions are slow-acting, virtually indestructable infectious proteins that...
    • cause brain diseases in mammals
    • *Prions propagate by converting normal proteins to prions
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Bio Final Prep - Viruses
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