Essential Question

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Essential Question

• What are germs and how do they affect us?

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• Virus is the Latin name for poison.

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• What is the one thing that all viruses have in
  common?
• All viruses enter living cells and use the cells
  machinery to produce more viruses.

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What do viruses infect?

• Cells of living things
• Viruses are specific to the cells they infect.
• The cell the virus infects is called a host cell.
• Any particle that causes disease is called a
  pathogen.

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What do viruses infect?

• Cells of living things
• Viruses are specific to the cells they infect.
• The cell the virus infects is called a host cell.
• Any particle that causes disease is called a
  pathogen.

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What is the size of a virus?

• Viruses are very small. (electron microscope)
• 17nm 100 nm (.00000004 inches)
• 950,000 viruses end-to-end would fit across a
  penny 9,500,000 viruses end-to-end would fit
  along the length of a pencil!
• SHAPE Viruses come in a variety of shapes
• Helical
• Polyhedral
• Spherical
• Spacecraft-like

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HELICAL VIRUS
Influenza Virus (Flu)
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POLYHEDRAL VIRUS
Lymantria dispar Multinucleopolyhedrosis Virus
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Define bacteriophage

• Viruses that infect bacteria.

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Describe the lytic cycle.

• 1. Virus enters the cell.
• 2 Virus takes over the host cell and starts
  making copies using the cells machinery.
• 3. Cell bursts.
• bad houseguest
• Animation

• Viruses that undergo this cycle are said to be
  virulentthis means they cause disease.

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• Viruses that undergo this cycle are said to be
  virulentthis means they cause disease.

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Describe the lysogenic cycle. (permanent
houseguest)

• 1. The virus enters the cell.
• 2. Viral DNA combines with host DNA forming a
  new set of genes. (provirus)
• 3. When the host cell replicates the cells DNA,
  it also replicates the provirus.
• 4. New virus particles are not assembled and the
  host cell is NOT destroyed.
• After many months, years, etc., the provirus may
  leave the hosts DNA and enter the lytic cycle.
• KEY The cell does not burst right away.
• Animation

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Name 5 diseases caused by viruses

• Chicken pox
• Mumps
• Rabies
• AIDS
• HIV
• Polio

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What is a retrovirus? Name a virus that is a
retrovirus.

• A retrovirus is a virus that makes DNA from RNA.
• HIV

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What is the function of a vaccine?

• Weakened or killed virus or viral proteins.
• Stimulates the body to create antibodies.
• Medications only provide relief from symptoms.

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Are viruses alive?

• Viruses are not alive. They do not have all the
  characteristics of life.

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HIV and AIDS

• Retrovirus
• HIV infects cells that help our body fight
  disease. (T4 cells or Helper T cells)
• Most people die from other infections.
• Transmitted through direct contact through bodily
  fluids.
• Spherical
• 120 nm (60 times smaller than a RBC)