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Viruses

Viruses. Something you don’t want to catch…. Viruses. 1. How do scientists classify things as living? Made of cells Has a metabolism to grow and reproduce Information stored in DNA 2. Are viruses alive?. NO!. Living or Nonliving?. NONLIVING. LIVING. Viruses.

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Viruses

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  1. Viruses Something you don’t want to catch…

  2. Viruses 1. How do scientists classify things as living? • Made of cells • Has a metabolism to grow and reproduce • Information stored in DNA 2. Are viruses alive? NO!

  3. Living or Nonliving? NONLIVING LIVING

  4. Viruses 3. What do viruses and living organisms have in common? • Both use nucleic acids to store genetic information in the form of DNA or RNA • Both change over time (evolve)

  5. Viruses 4. If viruses do not have their own metabolism to grow and reproduce, how do they survive? • By hijacking living cells and using their metabolism to grow and reproduce.

  6. There are 2 types of viral infections • Lytic infection- a virus enters a cell, makes copies of itself, and causes cell to burst . • Lysogenic infection- a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA.

  7. Lytic Cycle • Attaches to host (1) • Injects genetic material into host(2) • Cellular machinery duplicates genetic material and creates viral proteins (capsids, tail fibers) (3) • New viruses are assembled (4) • New viruses exit the cell by bursting the cellular membrane (5) • End result – more viruses made, cell dies • Viral Reproduction – Lytic Cycle

  8. Attachment Lytic Cycle • Viral Reproduction – Lytic Cycle Entry Release Replication Assembly

  9. Lysogenic Cycle • Attaches to host • Injects genetic material into host • Viral genetic material is inserted into host genome (6) • Viral genetic material lies dormant (6) • When cell reproduces, new copies have viral genetic information (7) • When virus is ready to exit dormant stage it will separate from cell’s DNA and enter Lytic cycle (8) • End result – more viral genome made, cell lives • Viral Reproduction – Lysogenic Cycle

  10. Lysogenic Cycle • Viral Reproduction – Lysogenic Cycle Attachment Entry Separation Insertion Reproduction

  11. Viral Reproduction Lytic Cycle • New viruses made • Cellular host dies Lysogenic Cycle • Genome copies made • Cellular host lives Viruses can use both cycles • Infect many cells with lysogenic • Create many viruses at once with lytic

  12. Lytic & Lysogenic Cycles • Viral Reproduction

  13. Virus Types • Bacteriophages = are viruses that attack bacteria • Retroviruses = viruses that use RNA to reverse transcribe DNA that integrates into the host genome. Example: HIV

  14. More Virus Types • What makes these viruses different from bacteria? THEY ARE NOT LIVING !

  15. CHECK POINT • This graphic shows a virus’ _____ _______. • Viral Reproduction • Viral Transription

  16. How do you treat a virus? • Remember you cannot treat a viral infection but you can prevent one by getting a vaccine.

  17. Vaccine A vaccine improves immunity to a particular disease.

  18. How do vaccines work? http://health.howstuffworks.com/adam-200097.htm • A vaccine contains a weakened strain of the microbe. • When injected into your body it stimulates your immune system to recognize it as foreign, destroy it, and remember it. • So if your body encounters the full strain later, it can easily recognize and destroy it!!!!!

  19. SUMMARY Important facts about viruses • Viruses must be produced within living cells • Viruses destroy the living cells they grow in • Viruses gain entry by specific receptors on the host cell

  20. Viruses • How do you catch many viruses? • What are your chances of catching a virus from someone in this classroom? Through body fluids.

  21. AIDS – acquired immune deficiency syndrome • Describes loss of immune system because of HIV • Caused by HIV - human immunodeficiency virus • makes helper T cells useless • Prevention • No vaccine • Limit transmission (use condoms) • Avoid transmission (use clean needles) • Viral Diseases - AIDS

  22. Viral Diseases – AIDS – HIV Replication

  23. Initial infection • Helper T cells rapidly decline • Viral genome rapidly increases • Clinical latency • Viral genomes lay mostly dormant in infected cells • AIDS • Rate of viral creation outweighs helper T cell creation • Death • Immune system too weak to fight common pathogens • Viral Diseases - AIDS

  24. Influenza (the flu) • Causes fever, fatigue, and respiratory infections • More severe than common cold, can be deadly • Viral Diseases - Influenza • Caused by a variety of influenza viruses • Change often, new vaccines yearly • Can blend with bird and swine strains to produce new viruses • Prevention • Seasonal vaccine • Limit transmission (wash hands) Image by NIAD [Public Domain]

  25. The Common Cold • Causes fever, fatigue, and respiratory infections • Less severe than influenza • Caused by a variety rhinoviruses • Over 200 different virus strains • Prevention • No vaccine • Limit transmission (wash hands) • Viral Diseases – Common Cold Image by Robin S [GNU]

  26. Hepatitis A • Causes inflammation of liver, jaundice appearance • Rarely results in liver failure • Caused by a hepatitis A virus • Carried through infected food or water • Prevention • Vaccine • Limit transmission (wash hands, food) • Viral Diseases – Hepatitis A Image by The CDC [Public Domain]

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