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Viruses How can you “kill” something that is not alive? How does a non-­‐ living “thing” cause disease? Venn •  Draw a venn •  Compare and contrast bacteria and viruses •  Keep in your notebook Hmwk: 19.2 READ/notes •  Quiz: •  1. What does “virus” mean in LaMn? •  2. What is the capsid of the virus? •  3. Bacteriphages infect ___________ •  4. The viral infecMon that causes a cell to burst is the ______________ infecMon. •  5. Viruses that contain RNA are called ________________ 6. T/F Viruses are made of cells. •  The following is just an overview of some familiar viruses. Causes “pink eye” Causes warts Causes the flu HIV-­‐ human immunodeficiency virus Virus-­‐size Viruses size
1. What is the structure of a virus?
2. A protein coat (capsid) that surrounds ONE
nucleic acid (DNA or RNA)
2. Sometimes an outer envelope
1. What is the structure of a virus?
2. Viruses ARE NOT made of cells!
3. No cell organelles or membranes
1. Who contributed to the major studies of virology? 2. famous virologists 3. Ivanowsky (1892) –worked with Tobacco mosaic disease (TMV) 4. tried to isolate disease organism – couldn’t b/c filter pores weren’t small enough 3. Stanley (1935) – isolated viral crystals – proved TMV was not bacteria 2. Edward Jenner (1796) -­‐ recognized immune response of milkmaids with cowpox to smallpox 2. Louis Pasteur (1880’s) -­‐ created rabies vaccine (less virulent virus –
injected to sMmulate immune system) 2. Jonas Salk (1955) & Sabin (1961) – created polio vaccine (shot & then oral) -­‐ Salk tested it on his family members Poliovirus 1. How do viruses reproduce? 2. Must use cell’s machinery , like ribosomes
3. Lytic cycle…infection quickly
3. Lysogenic cycle…infection later
LYTIC CYCLE-­‐ Sketch /label Step 1: virus a"aches to cells Step 2: virus injects nucleic acid into host cell Step 3: viral DNA or RNA takes over cell (like controlling the factory) Step 4: mRNA of host cell directs synthesis of viral proteins and nucleic acids Step 5: viruses break out of host cell (lysis) Step 6: viruses infect new host cells Lysogenic cycle Step 1. virus injects nucleic acid into host cell Step 2:viral DNA inserts itself into host cell’s DNA (prophage or provirus) Step 3: viral DNA remains inac7ve Step 4: cells divide & each cell has viral DNA * Lysogenic viruses become LYTIC at some Mme… 1. Retroviruses (how are these different from other viruses?) 2. Inject RNA – reverse transcriptase enzyme converts RNA to DNA – insert into host cell – (HIV) The dawn of HIV
A retrovirus causes AIDS
In May 1983: doctors at the Institute Pasteur in France reported that they had isolated
a new virus, which they suggested might be the cause of AIDS.
Barre-Sinoussi F. … and Montagnier L. (1983), 'Isolation of a T-Lymphotropic retrovirus from a patient
at risk for Acquired Immune Deficiency Syndrome (AIDS)', Science, May 20
In May 1983: doctors at the NIH in the US reported that a retrovirus virus related to
Human T cell Leukemia virus was present in patients with AIDS.
Gelman EP … and Gallo RC. (1983), “Proviral DNA of a retrovirus, human T-cell leukemia virus,
in two patients with’AIDS, Science, May 20
January 1985 It becomes clear that LAV and HTLV-III are the same virus and
The FDA licenses the first blood test for AIDS
http://www.avert.org/his81_86.htm
HIV STRUCTURE 1. What is a vaccine? •  2. a lessened form of the virus –  3. acMvates anMbody producMon http://www.pbs.org/wgbh/evolution/library/01/1/l_011_20.html
http://www.pbs.org/wgbh/evolution/library/10/4/l_104_05.html
http://www.hhmi.org/biointeractive/media/demo_hiv_test-sm.mov
1. Other 2. immune system makes AnMbodies in response to viral infecMons (anMbodies are Y shaped proteins specifically made to fit with the viral protein) -­‐ T-­‐cells (white blood cells maturing in Thymus gland) tell B – cells (white blood cells maturing in Bone marrow) to make anMbodies 2. HIV immunity – CD4 T-­‐cell site missing for aoachment LifeMme immuniMes form when exposed to a virus – chickenpox, measles, polio vaccine 2. immune system also produces Interferon (interferes with viral reproducMon) 2. Prions – glycoprotein without a nucleic acid – Madcow disease and Cruetzfeldt – Jacob disease-­‐ eat holes in the brain But what is
a retrovirus?
http://www.avert.org/his81_86.htm