• NOT classified in kingdoms or (Linnaeus system), no scientific names.

• How are they named?
• After the disease caused; or the tissue infected; code names ex: HIV; named after discoveror; or where discovered.

III. What is a Virus?

• Non cellular

A. Size: Much smaller than bacterium.

    *Between .1-.5mm or micrometers.

    *Only visible thru electron microscope.

B. Shape: Geometric System

C. Structure and Composition:

       1. Protein coat (capsid)-  outer.

       *Some animal viruses have a mucous    coating  (envelope) outside capsid.

       2. Genetic material (nucleic acid:DNA or RNA)

           RNA only is a retro virus.

• Transmission (1 difficult-10 easy like flu)
• Lethality (1 not deadly -10 deadly)

Fluidborne, airborne, food/waterborne, direct contact

V. Reproduction of Viruses

(1 thing that is life like about them)

A. Must reproduce inside a specific "host" cell.

   *Species specific.

   *Tissue specific.

 (Due to matching of surface proteins.)

B. Lytic Cycle (5 Steps)

     1. Recognition/Attachment

     2. Entry (Penetration) -nucleic acids & viral  enzymes inserted into host cell.

     3. Replication

           a. Viral enzymes "destroy" host cell DNA.

           b. Viral nucleic acid is used to synthesize new viral proteins. (Uses host cell organelles and bio-molecules.)

-Replicates its nucleic acids.

     4. Assembly-New virions are made with viral proteins, enzymes, and nucleic acids.

     5. Release (Lysis)<- means to burst -New virions burst out of cell. (50-200 virions)

C. Lysogenic Cycle

Ex: herpes, all poxes

   *Viral DNA is incorporated into host cell DNA as a provirus(prophage).

*Prior to cell division, the provirus is replicated along with host cell DNA.

   It will just attach itself on to a cell's DNA.

*Results in generations of cells containing provirus.

Problem is if cells containing the  provirus are triggered to enter lytic cycle. They will burst ALL cells with it at once.

Environmental triggers:

• Immune system
• Stress
• UV radiation
• Chemicals

A. Body's Defense System

 -interferon, killer T-cells: Programed to destroy viral infected cells with enzymes.

 -Protein produced by viral infected cells that "alerts" neighboring cells to increase defenses. (Paul Rever) "Viruses are coming!"

B. Drugs Which Interupt Virus Reproduction Ex: Drug Cocktail

 -Combination of 3 drugs used to "Slow Down" reproduction of viruses.

 -$ very expensive, side effects are brutal.

C. Vaccines, Ex: MMR shot, Flu Shot

 - Preventatives

 -Weakened/ "dead' version of the pathogen, that simulates immune system by making "memory" cells that will recognize future infections quickly.

Genetic Transformation

aka- genetic engineering, genetic recombination

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1. Get E.coli to take in plasmid.
2. Get E.coli to express genes on plasmid.

When expressed, it causes GFP to be made.

GFP =Green Floresent Protein.

HIC

(Hydrophobic Interaction Chromatography)