VIRUS Notes

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VIRUS Notes
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Definition

• Viruses are tiny particles unlike any other
  organism. A virus consists of genetic material
  such as RNA or DNA wrapped in a protein coat.

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Characteristics of Life

• Homeostasis
• Nutrition
• Transport
• Respiration
• Synthesis
• Growth
• Excretion
• Regulation
• Reproduction
• Is a virus living?

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Is it living?

• No, because a virus can not reproduce on its own.
  It needs a host cells.

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How does a virus size relate to the size of the
cell?

• Viruses are much smaller than a cell and that is
  why they can easily get into a cell

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How are viruses characterized?

• Characterized as
• Plant
• Animal
• Bacterial virus

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What are the two parts that comprise a virus?

• Nucleic Acid Core (either RNA or DNA)
• Protein Coat called a capsid

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Shapes of Viruses

• 1. Rod shaped (tobacco mosaic virus)

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Shapes of Virus

• 2. Polyhedral (Mumps)

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Shapes of Virus

• 3. Helical (Herpes)

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How does a DNA virus replicate?

• DNA virus produces RNA (transciption)
• RNA directs production of viral proteins
• OR
• Viral DNA combines with host cells DNA (either
  plant or animal)

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How does RNA virus replicate or reproduce itself?

• Once inside the host, an RNA virus directs the
  host cell to produce proteins
• OR
• Viral RNA may make DNA

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Retrovirus

• Virus that has RNA as its genetic material
• Example is HIV

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Bacteriophage

• Virus that attacks a bacterial cell
• Two types of infection
• Lytic Cycle
• Lysogenic Cycle

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Lytic Cycle

• Bacteriophage attaches to host cell and injects
  its DNA
• Foreign DNA produces more proteins in the host
  cell
• Causes cell to lyse (or break open) and the
  virus/phage is released into the hosts body

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Lytic Cycle
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Lysogenic Cycle

• Phage injects DNA into the host cell
• Foreign/phage DNA integrates itself into a
  chromosome
• Bacteria reproduces

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Lytic vs.Lysogenic Cycle