quiz3prac

quiz3prac - MIT Biology Department 7.012: Introductory...

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7.012 Quiz 3 practice Quiz 3 on Friday, November 12th 10 – 11 AM Review Session Wednesday 11/10 from 7-9 pm Tutoring Session Thurs. 11/11 from 4-6 pm MIT Biology Department 7.012: Introductory Biology - Fall 2004 Instructors: Professor Eric Lander, Professor Robert A. Weinberg, Dr. Claudette Gardel
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2 Question 1 A) You infected mice with mouse mammary tumor virus (a retrovirus). After a period of time, most infected mice had developed breast tumors, whereas uninfected mice did not. You isolated cell lines from over 50 independent tumors. You demonstrated that all of these lines had virus integrations in the same chromosomal location. Can one conclude that the virus integrates into cellular DNA at only one site? Explain. B) The ras oncogene is involved in a variety of human and animal cancers. DNA was isolated from a number of normal and cancerous tissues. -Cellular DNA was digested with Eco RI. -Digested DNA was separated by gel electrophoresis and transfered to a nitrocellulose membrane. -The membrane was probed with the radioactive labelled cloned ras DNA and then the membrane was exposed to x-ray film. -The resulting autoradiograph is shown below. 1) white blood cells from a healthy human 2) human lymphoma cells (cancerous) 3) human bladder carcinoma cells (cancerous) 4) human sarcoma cells (cancerous) 5) blood from a healthy mouse 6) mouse myeloma cells (cancerous) 1 2 3 4 5 6 10 kb 5 kb 1 kb more than 2 copies/genome 2 copies/genome 1 copies/genome
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3 Question 1 continued a) How do you explain the presence of sequences complementary to the oncogene in the DNA from healthy human and mouse samples? Why don't they have cancer? b) Why is the hybridizing band from sample 1 a different size than that from sample 5? c) For each cancer examined above, based on the autoradiogram, choose the most likely mechanism of transformation and explain your choice: 1) point mutation within the gene 2) chromosomal rearrangement involving the gene 3) gene amplification 4) oncogenic retroviral insertion. Question 2 You are studying the cell cycle in haploid yeast cells. You isolate a cell that is a temperature-sensitive cell division cycle ( cdc ) mutant, cdcX -. cdcX - grows normally at 25 ° C, but arrests at 36 ° C at the point in the cell cycle where the expression of the normal cdcX gene is required. To determine where in the cell cycle expression of cdkX is required, you design experiments based on the following facts: 1) The drug nocodazole arrests, but does not kill yeast in mitosis (M phase). 2) Cell density can be measured to determine if the yeast cells have completed a cell division. For your experiments: You incubate cdkX - cells at 25 ° C with nocodazole until all the cells are synchronized. You then shift the cells to 36 ° C and remove the nocodazole. The cells divide once and then arrest.
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This note was uploaded on 11/11/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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quiz3prac - MIT Biology Department 7.012: Introductory...

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