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Unformatted text preview: Name_____________________________________ Section_______ TA_____________ 1 2010 7.012 Problem Set 6 Please print out this problem set and answer the questions on the printout. Answers to this problem set are to be turned in at the box outside 68-120 by 1:15 pm, Friday November 12 th . Question 1 Working as a UROP, you are asked to complete some experiments that involve several different viruses, including R ous s arcoma v irus retrovirus (RSV) . After a long day, you place your viral samples in the refrigerator, but you forget to label them. As a 7.012 student, you have recently heard Prof. Weinbergs lecture on cancer viruses, so you know you can identify the tubes. a) The type of genomes found in viruses can vary. Some viruses have single (ss) or double-stranded (ds) DNA genomes; others have single (ss) or double-stranded (ds) RNA genomes. Given the data below, identify all possible types of genomes for each virus. Virus % A % T % U % C % G Type of genome, i.e., ds-DNA 1 18 18 0 32 32 2 25 0 25 25 25 3 35 15 0 15 35 The experiment in part (a) allows you to identify all of the unlabeled viruses except 2. The remaining 2 viruses are both single-stranded RNA viruses. You know that one virus is the Norwalk virus, and the other is RSV. The Norwalk virus causes intestinal illness. Norwalk and Norwalk-like viruses are increasingly being recognized as leading causes of food borne disease in the United States. The Norwalk virus is a + strand RNA virus that is surrounded by an icosahedron-shaped capsid composed of two different polypeptides. RSV is a retrovirus that also has a + strand RNA genome that encodes four genes; gag (encodes the capsid protein), pol (encodes the reverse transcriptase), env (encodes the envelop glyco-protein) and src (encodes a tyrosine kinase enzyme). b) Given the information above i) Do you expect that the Norwalk virus would encode its own RNA polymerase? Explain why or why not. ii) Reverse transcriptase is considered which of the following? A DNA directed DNA polymerase A DNA directed RNA polymerase A RNA directed DNA polymerase A RNA directed RNA polymerase iii) Why is it essential that the RSV encodes Reverse transcriptase? c) You have a cell line that can be infected by these two viruses. What is a cell line? Name_____________________________________ Section_______ TA_____________ 2 Question 1, continued To determine which virus is which, you grow your cell line on two identical plates (plates A and B) in a medium that contains C 14-labeled uracil, P 32...
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- Fall '10