midterm 2 - Molecular Genetics Midterm II, Spring quarter...

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Molecular Genetics Midterm II, Spring quarter 2007 Name_________________________________ Page 1 Total points on page ______________ It is your responsibility to make sure all answers are legible and that we can determine what you wish your final answer to be. If you have a question, raise your hand and wait for Dr. Oakley or a graduate teaching associate. Do not get up from your seat . Students will not be allowed to leave during the first 30 minutes of the exam period except in cases of emergency. Students will not be allowed to take the exam if they arrive more than 30 minutes after the beginning of the exam period. All exams must be handed in at the end of the exam period or before. There will be no extra time for late arrivals. Please write your name on each page and the last four digits of your social security number on the back of this page . If you need extra space, please use the back of the page and indicate that you have done so. There are 26 questions on 9 pages (including this page) for a total of 104 pts (essentially 4 pts extra credit although there is no question marked “extra credit”).
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Molecular Genetics Midterm II, Spring quarter 2007 Name_________________________________ Page 2 Total points on page ______________ 1. In the experiments of Taylor, Woods and Hughes, root tips of the broad bean Vicia faba were grown for one cell cycle in the presence of 3 H Thymidine, and when the cells entered mitosis all chromatids were radioactively labeled. If DNA replication were conservative, what fraction of the chromatids would have been labeled? (3 pts) Answer: 1/2 2. A number of temperature-sensitive mutations that affect DNA replication have been isolated in E. coli and they have been instrumental in determining the mechanism of DNA replication in this organism. Temperature-sensitive mutations are mutations in a gene that alter the amino acid sequence of the protein product of the gene such that the product functions normally at “permissive” temperatures, but does not function at “restrictive” temperatures. 2.1. Predict the phenotype of a temperature-sensitive dnaG (primase) mutant at a restrictive temperature. Circle the best answer. (3 pts) a) Little or no DNA synthesis would occur. Answer: a b) A great deal of DNA synthesis would occur, but Okazaki fragments would remain after synthesis. c) DNA synthesis would occur normally, but the error frequency during DNA replication would be much higher than normal. d) DNA synthesis would occur normally and the error frequency during DNA replication would be normal. 2.2. Predict the phenotype of a temperature-sensitive lig (DNA ligase) mutant at a restrictive temperature. Circle the best answer. (3 pts) a) Little or no DNA synthesis would occur. Answer: b b) A great deal of DNA synthesis would occur, but Okazaki fragments would not be joined together after synthesis.
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This note was uploaded on 10/21/2008 for the course MOL GEN 500 taught by Professor Rogers during the Spring '07 term at Ohio State.

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midterm 2 - Molecular Genetics Midterm II, Spring quarter...

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