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Virus - PowerPoint PPT Presentation

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Virus!. Not Alive, But Still Deadly…. Bacteriophages or Virus?. Bacteriophages or Virus?. Bacteriophages attack bacteria (prokaryotes) viruses attack eukaryotic cells (animal and plant cells).

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Not Alive,

But Still Deadly…

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Bacteriophages or Virus?

  • Bacteriophages attack bacteria (prokaryotes)

  • viruses attack eukaryotic cells (animal and plant cells).

  • Viruses and bacteriophages take over cells and use the host cell's organelles to make more of their own parts.

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Viral Size and Structure

  • Virus shape is determined by the DNA/RNA and protein coat covering its genome (DNA/RNA)

  • Basic structure:

    • Capsid: Protein coat

    • Nucleic acid core: RNA or DNA

      • Genome can be single or double stranded

      • Helps determine shape of virus

    • Lipoprotein coat

      • Envelopes (covers) capsid in some viruses

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Virus Categories (Examples of Viruses)

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Virus Categories

  • DNA viruses – stable, do not mutate rapidly

    • Single-stranded or double-stranded

    • Includes Smallpox and Hepatitis B

  • RNA viruses – mutate rapidly, unstable

    • Single-stranded or double-stranded

    • Includes HIV and Rhinovirus

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The Lytic Cycle

  • Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell.

  • The viral nucleic acid takes over protein synthesis, creating new viruses.

  • The host cell bursts, lyses, releasing the newly formed viruses.

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The Lysogenic Cycle

  • Nucleic acid of virus becomes part of the host cell’s chromosome

  • Nucleic acid remains in the cell in this form for many generations

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  • HIV is a retrovirus that leads to AIDS

  • The virus kills or damages cells of the body's immune system, progressively destroying the body's ability to fight infections

  • 25 million people worldwide have died from AIDS

  • A combination of at least three drugs is recommended to suppress the virus from replicating and boost the immune system

  • There is no cure for HIV and AIDS

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  • Caused by the varicella-zoster virus (VZV) and common in children under 12

  • Highly contagious, itch rash

  • Children can be vaccinated against the disease

    • Some children may still get chickenpox though

    • Those that have had chickenpox have a natural immunity to the disease

  • VZV can lie dormant within the body and cause shingles later in life

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  • Two common types: Influenza A and Influenza B

  • Flu Symptoms include:

    • fever (usually high), headache, extreme tiredness, dry cough, sore throat, runny/stuffy nose, muscle aches

    • Nausea, vomiting, and diarrhea can occur but are more common in children

  • 5% to 20% of U.S. residents will get influenza each year

    • 36000 people on average die from influenza-related causes

    • 200,000+ will admitted to the hospital as a result of influenza-related causes.

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Smallpox and Vaccination

  • Edward Jenner is credited with the first vaccination against smallpox

  • Country-lore suggested that people who caught cowpox from their cows did not get smallpox

    • Jenner transferred material from the pocks of a dairymaid to James Phipps, the 8 year old son of his gardener

    • James became mildly ill from cowpow

  • Weeks later, Jenner infected James with smallpox

    • No infection now or during future trials

  • The first vaccination published was a success!