Exam3key.07 - Bio 221 Name_Key_ Exam 3 Please tear off the...

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Name________ Key _________________ Exam 3 Please tear off the first page of your exam and turn it in along with your scantron sheet. You may keep the rest of the exam. Short answer. 5 points each. Use the back of the page if necessary. 1. The diagrams below represent two microtiter plate wells. A patient is being tested for exposure to hepatatis B. Sketch and label the components of an indirect ELISA test if (A) the patient has hepatitis B, and (B) the patient does not have hepatitis B. 2. Though we no longer assume that they must all be satisfied, Koch’s postulates are still important in figuring out what organism causes a disease. List Koch’s postulates. (1) Organism must be isolated from every case of the disease (2) Organism must be grown in pure culture (3) Organism must cause same disease in test host (4) Same organism must be isolated from diseased test host 3. Why are scientists concerned that overuse of a single antibiotic might select for multiple antibiotic resistance in bacteria? How can multiple antibiotic resistance spread so quickly within a bacterial population? The presence of R-plasmids in a population means that selection for any of the antibiotic resistances on the plasmid selects for them all . R-plasmids carry fertility functions, and can spread from cell to cell by horizontal gene transfer . So the capability to spread, coupled with the presence on the plasmid of many antibiotic resistance genes means that the whole population can become resistant to many antibiotics even if only one antibiotic is used. 4. Explain how the process of antigenic shift can alter the influenza virus. What is usually the result of such an antigenic shift? Antigenic shift occurs when more than one influenza virus, with different H and N types , infect the same cell simultaneously. Since influenza is segmented , all 16 segments from the two viruses are present in the host cell. The new virus can be assembled by randomly combining the RNA fragments from both “parent” strains . The result is a virus with a completely new H and/or N type combination . If the human population has low immunity to such a virus, a flu pandemic ensues. 5. Describe the progression of a typical case of cholera. Include how the organism is transmitted, how it causes illness, the typical course of the illness, and how it is treated. Transmitted in infected food or water (large dose needed). Some organisms survive stomach acid and bind to intestinal epithelial cells. Secrete AB toxin . B part binds to epithelial cells. A part ADP-ribosylates a regulatory protein. Excess cAMP produced . Fluid secreted into gut as a result of cAMP. Death by dehydration from massive water loss. Treat by oral replacement of electrolytes and water . A:
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This note was uploaded on 04/07/2008 for the course BIOL 221 taught by Professor Walter during the Spring '08 term at Purdue University-West Lafayette.

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Exam3key.07 - Bio 221 Name_Key_ Exam 3 Please tear off the...

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