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Viruses

Viruses. SB3. Students will derive the relationship between single-celled and multi-celled organisms and the increasing complexity of systems. d . Compare and contrast viruses with living organisms. Essential Question. How do viruses compare to living organisms?. What is a virus?.

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Viruses

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  1. Viruses SB3. Students will derive the relationship between single-celled and multi-celled organisms and the increasing complexity of systems. d. Compare and contrast viruses with living organisms.

  2. Essential Question How do viruses compare to living organisms?

  3. What is a virus? A virus is a non-living infective agent that replicates within the cells of living hosts. • Common characteristics of all viruses include: • Not a living organism • Must attack a living cell in order to reproduce • Can have a genetic material made of DNA or RNA

  4. The tiniest viruses are 20 nm in diameter. (smaller than a ribosome). • The largest virus known is the Megavirus, having a capsid diameter of 440 nm (10-20 times larger than most viruses)

  5. The Structure Of a Virus • Viruses are composed of a core of nucleic acid • The Nucleic acid core is surrounded by a protein coat called a capsid • Thenucleic core is either made up of DNA or RNA but never both

  6. Viral Structures How do viruses compare to living organisms?

  7. Reproduction • Viruses are obligateintracellular parasites that can reproduce only within a host cell. • TheyDO NOT have • Enzymes for metabolism • Do not have ribosomes • Do not have the equipment to make proteins

  8. The Lytic Cycle Culminates in the death of the host cell Virulent viruses reproduce only by lyticcyle. Natural selectionfavors bacterial mutations with receptor sites that are resistant to a particular phage or that have restriction enzymes to destroy the phages. The Lysogenic Cycle Replication of the viral genome without destroying the host cell. A temperate virus may reproduce by either cycle. Lambda virus: resembles T4 but only has a single short tail fiber Reproduction occurs using Lytic or Lysogenic cycles

  9. Common Viruses Influenza The Flu Varicella zoster Chicken Pox/Shingles

  10. Common Viruses Flavivirus West Nile Virus Lyssavirus Rabies Virus

  11. Common Viruses Hepadinavirus Hepatitis B Picornaviridae Polio Virus

  12. Deadly Viruses Ebola sudan Ebola zaire

  13. Deadly Viruses Variola Virus Small Pox Marburg Virus

  14. Retroviruses Retroviruses are viruses composed, not of DNA but of RNA. Retroviruses have an enzyme, called reverse transcriptase, that gives them the unique property of transcribing their RNA into DNA after entering a cell. The retroviral DNA can then integrate into the chromosomal DNA of the host cell, to be expressed there. Retroviruses are the only viruses in the world that can transform RNA back into DNA. HIV (human immunodeficiency virus) is a lentivirus that causes AIDS (acquired immunodeficiency virus). This failure of the immune system allows life threatening opportunistic infections and cancers to thrive.

  15. The Hot Zone The Hot Zone: A Terrifying True Storyis a best selling, 1994 non-fiction bio-thriller by Richard Prestonabout the origins and incidents involving viral hemorrhagic fevers, particularly ebolaviruses and marburgviruses. The filoviruses, Ebola virus, Sudan virus, Marburg virus, and Ravn virus are Biosafety Level 4 agents. Biosafety level 4 agents are extremely dangerous to human because they are very infections, have a high case-fatality rate, and there are no known treatments or cures. We will be reading an excerpt from the first section of the book, regarding the Marburg virus. The excerpt details Marburg’s symptoms as manifested in the character “Charles Monet.” We will discover the origin of the virus as well as its gruesome symptoms.

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