Chapter 19

  1. Structure of Virus
    • 20nm - not cell
    • infect particel consisting of nucleic acid enclosed in a protein coat and or  some by membranous envelope
    • Either DNA virus or RNA virus base on the kind of nucleric acid that makes up its genome
  2. Capsid
    • protein shell enclosing the viral genome
    • built from a large number of protein subunits capsomeres
    • rodshaped olyhedral or more complex in shape
    • Ex Tobacco mosaic = rigid rod shaped
  3. Viral envelopes
    • membranous envelopes surrounds the casids of influenza virus and other virus
    • derived from membranes of host cell, contain host cells phosholipids and membrane proteins, glycoproteins
    • Heres virus get membrane from nuclear envelope
    • Animal virus has it but not much of bactoriophage
  4. Bacteriophages/ phage
    • virus that infect bacteris
    • named T1 - T7
    • T2,4,6 have similar structure - capsids have elongated icosahedral heads enclosing their DNA -> protein tail attach to head
  5. Host Range
    • virus can infect cells of only a limited number of host species
    • lock and key fit
    • virus can infect specific species or tissue base on their host range.
  6. Viral Repcative Cycle
    Virus Enter cell with its DNA and Capsid - Host enzyme relicate the viral genome -> change into mRNA to make proteins -> genome and caside protein reassemble to make new virus - exit
  7. Lytic Cycle
    • cycle that cuminates in death of the host cell
    • last stage of infection
    • virulent phage:
    • Attachment -> inject DNA -> Synthesis of viral genomes and proteins -> assembly -> release
  8. Restriction Enzyme
    restricts the ability of the phage to infect  the baterium once it identify the DNA as foreign
  9. Lysogenic Cycle
    • allows replication of the the phage genome without destrying the host
    • temperate phages - capable of using both modes of replicating within a bacterium                
    • Prohage - Phage DNA integrates into bacterial chromosome (different from lytic cycle) -> it may affect cells phenotype
  10. Retroviruses(classVI)
    • RNA animal virus with the most complicated  replication cycles
    • has reverse transciptase - enzyme transcribes an RNA template to DNA. RNA -> DNA flow, the opposite of the usual direction.
    • Causes HIV and AIDS
  11. HIV Replicative cycle
    Reverse transcrtase molecule released into cytoplasm - > new viral DNA -> provirus - intergrated viral DNA that never leaves the host cell.
  12. Emerge of Virus
    • Mutation
    • Dissemination
    • Spread of virus from animal
    • Influenza A- infect both animals and human
  13. Hemagagglutinin
    • 16 differnt types
    • helps flu virus to attach to host cells
  14. neuraminadase
    • 9 types
    • enzymes that help release virus particles fom the cell
  15. Plant's Horizontal vs vertical Transmission
    • Horizontal - plant infect by an external virus
    • Vertical- inheirit virsu from it parent plants
  16. Viroid
    simple virus made of RNA molecules, inect plants
  17. Prion
    • infectious proteins
    • causes degenerative brain disease in animal
    • EX;mad cow, Creutzelub Jacob
    • indestructible, 10 years incubation period
    • convert other cell proteins to prion protein
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Chapter 19