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Chapter 19 Viruses (Concept 19.2 (Bacterial Defense Against Phages…

- - - - Can prevent certain viral illness
      - Viral infections cant be treated with antibiotics
      - Antiviral drugs can help treat but not cure viral infections
  - - - Can be disseminated from a small isolated human population & can spread around the world
      - 3/4 new human diseases originate by spreading to humans from animals
      - RNA viruses have unusually high rates of mutation
    - - New roads into a remote area
      - The use of Insecticides and mosquito nets may help prevent the spread of disease
      - Global climate change may allow mosquitoes to expand their range
  - - - Horizontal - entering through damaged cell walls
      - Vertical - Inheriting the virus from a parent
- - - - Mosaic Coloration on leaves
      - Spreads through the sap
  - - - DNA ( single or double stranded)
      - RNA ( single or double stranded)
  - - - Polyhedral
        
        Iscosahedral virus
      - More complex shapes
      - Rod shaped
        
        Helix, Helical Virus
      - Made up of capsomers
      - Protein shell
    - - Membrane proteins
      - Proteins of viral origins
      - Host cell phospholipids
      - Glycoproteins of viral origin
      - Membrane of host cell
    - - replicates inside bacteria
      - Infects bacteria
- - - - Uses tail to inject DNA
      - Fusion of Viral envelope w/Plasma membrane
    - - Creates more viruses to infect more cells
  - - - The lytic Cycle
        
        Kills the host cell
        
        Last stage of infection
        
        Bacterium breaks open & releases the new phages
        
        Virulent phage - Only replicates by lytic cycle
      - The Lysogenic Cycle
        
        Allows replication without destroying host cell
        
        Temperate Phages - Phages capable of using both cycles
        
        Prophage - Viral DNA inserted into host cell
        
        An environmental switch can trigger it to go into lytic mode
  - - - Viral Glycoproteins on the envelope bind to receptors on host cell
      - Made of the host cell's plasma membrane as the viral Capsids exit
  - - - Remains a permanent resident of the host cell