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Notes - Viruses

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  • 1. Viruses The word virus means “poison” in Latin.
  • 2. Introduction
    • Influenza pandemic of 1918
    • Smallpox in the 18 th and 19 th century.
    • AIDS statistics…
  • 3. Viral Diseases
    • Common Cold
    • Flu (influenza)
    • Mumps
    • Measles
    • Smallpox
    • Chicken Pox
    • Hepatitis
    • Warts
  • 4. More Viral Diseases…
    • Cold Sores
    • Polio
    • AIDS
    • Bronchitis
    • Viral Pneumonia
    • Mononucleosis
    • West Nile Virus
    • Rabies
  • 5. How are viral illnesses treated?
    • Some have a vaccine to protect you.
    • Rest, plenty of fluids and time…
    • Sometimes an antibiotic is given to prevent a secondary infection.
  • 6. Germs are everywhere. How can you avoid being infected?
    • Wash your hands !!!
    • The 3 most common places to get germs:
      • #3 Door knob
      • #2 Computer mouse
      • #1 Shopping cart handles
      • http://www.youtube.com/watch?v=MWQ86R-aT-I
      • http://www.youtube.com/watch?v=RHqNk8_rOHk&feature=related
  • 7. History of Vaccines
    • 1796 – Edward Jenner (England)
      • Took infected matter from a sore on the hand of local milkmaid who had cowpox .
      • He rubbed it into small incisions on the arm of an 8 year old boy named Edward Phipps.
      • The boy developed a cowpox sore on his arm.
  • 8. 6 weeks later:
    • Jenner took some infected matter from a victim of smallpox and rubbed it into incisions made in Phipp’s arm again.
    • The boy remained healthy!
      • Jenner produced a vaccine for smallpox .
  • 9.  
  • 10. Louis Pasteur - 1884
    • Produced a weakened infective material from rabid dogs that was used as a rabies vaccine .
    • First used on a young boy who had been bitten by a rabid dog.
  • 11. Rabies symptoms
    • After a symptom-free incubation period that ranges from 10 days to a year or longer (the average is 30 to 50 days), the patient complains of malaise, loss of appetite, fatigue , headache , and fever . Over half of all patients have pain (sometimes itching) or numbness at the site of exposure. They may complain of insomnia or depression .
    • Two to 10 days later, signs of nervous system damage appear, hyperactivity and hypersensitivity, disorientation , hallucinations, seizures, and paralysis . Death may be sudden, due to cardiac or respiratory arrest, or follow a period of coma that can last for months with the aid of life-support measures .
  • 12.  
  • 13. Jonas Salk - 1953
    • Created a polio vaccine .
    • He actually killed the active form of the virus and used it as a vaccine.
      • 1952 – 57,000 cases of polio.
      • 1957 – virtually no cases.
  • 14.  
  • 15. Albert Sabin - 1960
    • Treated the polio virus to weaken it.
    • Produced a longer lasting immunity to polio than the Salk vaccine .
  • 16. Vaccinations : artificial immunity
    • 1. Inject a dead or weakened form of the virus (called an antigen .)
    • 2. Your body produces antibodies .
    • 3. The antibodies recognize the protein coat of the virus and hold it as it enters the body.
    • 4. Macrophage (a type of white blood cell) surround and digest the virus.
    • 5. You are now immune to this virus.
  • 17.  
  • 18. macrophage engulfs antigen by phagocytosis.
  • 19. Definitions:
    • Antigen – A substance that stimulates the production of antibodies.
    • Antibodies – A substance produced by plasma cells (in the blood) in response to specific antigens. They “hold” the antigen until white blood cells (phagocytes) surround and destroy it.
  • 20. Definitions cont…..
    • Vaccines – a commercially produced antigen of a particular disease.
    • It is not as “strong” as the actual disease itself.
    • Passive immunity – Babies receive antibodies from their mother.
    • It is temporary: it usually lasts for only 6-12 months.
  • 21. More definitions…
    • Pathogen – an agent that causes disease.
  • 22. Discovery of a Virus - 1933
    • Read pages 455-456 in textbook.
  • 23. Size of a virus
    • Much smaller than any cell.
      • Smallest is 17 nm (.000000017 meter) or 17 billionth of a meter! (nm = 10 -9 meter)
      • The largest is 100 nm (.0000001 nm) or 1 ten millionth of a meter.
      • Barely visible in an electron microscope.
      • http://www.cellsalive.com/howbig.htm
  • 24. Composition of a Virus
    • A strand of nucleic acid (DNA or RNA) surrounded by a protein coat known as a capsid.
    • It may also have an outer “envelope” that it has taken from a host cell.
    • It is the shape of the capsid or outer envelope that our immune system recognizes.
  • 25. Is a virus a living organism?
    • Living things vs. Virus
    • Made of cells Not a cell
    • Metabolism No metabolism
    • Use energy No cell respiration
    • Grow/develop No growth or development
    • Definite life span Life span?
    • Reproduce Need host cell to reproduce
    • Respond to stimuli “Inert” (inactive)
  • 26. Bacteriophage - “bacteria eater”
    • See page 457 in textbook.
  • 27. Lytic Cycle – 5 steps
    • Step 1 – Attachment – Virus attaches to a specific receptor site on a cell.
    • Step 2 – Penetration – Virus enters the host cell
    • Step 3 – Replication – Viral DNA and protein is copied.
    • Step 4 – Assembly - DNA and protein is assembled into a virus.
    • Step 5 – Release – Viruses rupture the cell membrane and are released to infect other cells.
    • http://biology.about.com/gi/dynamic/offsite.htm?site=http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/adlyt.html
  • 28. Lysogenic Cycle
    • Same as the lytic cycle but the viral DNA becomes incorporated into the host cell’s DNA.
    • It lies “dormant” until a later date.
    • http://student.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/lysolc.html#si
  • 29. Viral Subunit Reassortment
    • Two strains of a virus infect a cell at the same time.
    • The nucleic acid (DNA or RNA) mix to create new combinations .
    • New viruses are produced.
    • *It is believed this happens with cold and flu viruses commonly.
    • http://www.hhmi.org/biointeractive/animations/subunit/sub_middle_frames.htm
  • 30. Gene Therapy – A useful purpose of a virus
    • The harmful DNA is removed from a virus.
    • A “helpful” strand of DNA is inserted in its place.
    • Allow virus to deliver the genes to their target cells.
    • http://www.edu365.cat/aulanet/comsoc/Lab_bio/simulacions/GeneTherapy/GeneTherapy.htm
  • 31. Problems with gene therapy:
    • Locating the correct cells.
    • Genes accidentally spliced in the wrong place.
    • May trigger a nearby oncogene (cancer causing gene.)
    • May cause too much of something to be produced.
    • May cause a severe immune response.
  • 32. Current Research with gene therapy:
    • What diseases could be treated with gene therapy? ( From AMA website.)
    • About 4,000 diseases have been traced to gene disorders. Current and possible candidates for gene therapy include cancer , AIDS , cystic fibrosis , Parkinson’s and Alzheimer’s diseases , amyotrophic lateral sclerosis ( Lou Gehrig's disease ), cardiovascular disease and arthritis .

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