20182-2010-finalKEY

20182-2010-finalKEY - NAME: Lab Section_ PLEASE WRITE YOUR...

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NAME: 1 Lab Section______________ PLEASE WRITE YOUR NAME ON EVERY PAGE OF THE EXAM. BIOS 20182 2010 Exam 2 There are 7 questions. 100 points total. You have 2 hours. Budget your time.
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NAME: 2 1. (10 points total) In a transduction experiment the donor strain is c+ d+ e+ and the recipient was c- d- e-. The selection was for c+. Selected colonies were then scored for the d and e markers. The data were as follows: Class Genotype Number of colonies 1 c+ d+ e+ 57 2 c+ d+ e- 76 3 c+ d- e- 365 4 c+ d- e+ 2 TOTAL 500 a. (5 points) Calculate the co-transduction frequencies for c-d and c-e b. (5 points) Which two markers are closest together? c-d cotransduction = (57+76)/500 X 100 = 26.6% c-e = (57+2)/500 X 100 = 11.8% c-d are closer together.
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NAME: 3 2. (15 points total) In addition to studying the lac operon, Jacob and Monod carried out related experiments to study the process of lambda phage induction from lysogenic strains. In one famous experiment, they mated an Hfr strain that was lysogenic for lambda with an F - strain that was not a lysogen. They plated their mating mixtures on lawns of bacteria and found that by 30 minutes later, the mating mixture formed plaques of lambda phage. They did not see any plaques if the Hfr was plated directly on a lawn of bacteria without prior mating. The induction of phage they observed did not depend on the S.O.S. response. Furthermore, it occurred when they used a recA mutant recipient. Because the induction they saw in the initial experiment required mating, they called the phenomenon “zygotic induction.” Given this information, can you formulate a hypothesis for why lambda induction occurs as a result of mating? Your answer should include a specific mechanism involving the interaction of protein and DNA. In his memoir, Jacob said he had a revelation (while attending a movie) that the mating experiments he was doing to study the lac operon and those he was doing to study lambda phage induction, could be explained by the same type of regulatory mechanism. No lambda repressor protein is present in the cytoplasm of the recipient cell to inhibit expression of lambda genes. When the lambda genome is transferred by the Hfr into the recipient, lambda genes are expressed leading to production of phage particles and lysis. This is analogous to the PaJaMo experiment in which lacZ was transiently expressed after mating when the recipient was a lacI lacZ double mutant.
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NAME: 4 3. (25 points total, each subsection=5 points) You want to study the S.O.S. response in bacteria. You are given a strain that is a lambda lysogen and also carries a copy of the dinB gene in which the dinB coding sequence is replaced by the lacZ coding sequence. The altered gene is a fusion gene in which
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This note was uploaded on 02/09/2011 for the course BIOS 20182 taught by Professor Lahn during the Spring '11 term at UChicago.

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20182-2010-finalKEY - NAME: Lab Section_ PLEASE WRITE YOUR...

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