quiz2_final

quiz2_final - 7.014 Quiz II 3/18/05 Your Name: _ TA's Name:...

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7.014 Quiz II 3/18/05 Your Name : _________________________________ TA's Name: Write your name on this page and your initials on all the other pages in the space provided. This exam has 10 pages including this coversheet. Check that you have pages 1-10. Genetic code and the structures of the amino acids can be found on page 10. This exam has 4 questions. Read all questions before starting to write. Write your answers as clearly and precisely as possible in the space provided. This is a closed book exam. Question Value Score 1 29 2 30 3 25 4 16 TOTAL: 100
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Name:________________________________________ TA:____________________ 2 Question 1 (29 points) Barney is an alien. On his ship, hidden in the Stata building, you find alien bacteria that metabolize wood. You call this species A. termiticus , and call your original strain BLT (for “Barney’s little termiticus”). You subject a sample of BLT to mutagens, and isolate a new strain that no longer metabolizes wood. You conclude that you have succeeded in disrupting at least one gene necessary to metabolize wood. You call the mutant strain M. You mix a sample of M with a sample of heat-killed wild type BLT, and the resulting strain metabolizes wood. You summarize your data in the following table: Strains Metabolizes wood? BLT Yes Heat-killed BLT No M No Heat-killed BLT +M Yes a) Did the content of any of the BLT or M cells change in the experiment? If yes, which cells underwent the change, and what change occured? If not, explain why there was no change. You plan to characterize the alien genetic material. You start by breaking some A . termiticus cells open to determine their molecular composition. You find that they contain various small molecules, carbohydrates, lipids, and two other macromolecules, A and B. In order to determine which macromolecule is the carrier of genetic information, you repeat your previous experiment, but include test tubes where you treat the sample of the heat-killed BLT with either an agent that destroys macromolecule A (A-ase) or macromolecule B (B-ase). You find the following results (including the repeat of your previous experiment in the first 4 lines): Strains and agents Metabolizes wood? BLT Yes Heat-killed BLT No M No Heat-killed BLT +M Yes A-ase treated heat-killed BLT +M Yes B-ase treated heat-killed BLT +M No b) Which molecule is the carrier of genetic information in A. termiticus ? Justify your answer.
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Name:________________________________________ TA:____________________ 3 Question 1, continued Next, you set out to determine the structure of the alien genetic material molecule. You first determine that it has six types of bases that you name S, V, W, X, Y, Z. You further determine that the alien cell’s content of S is the same as its content of each of X and Z; and that the content of V is the same as its content of each of W and Y. When you determine the structure of this molecule by X-ray crystallography, you are not surprised to find that the molecule consists of 3 interacting strands.
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This note was uploaded on 05/02/2009 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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quiz2_final - 7.014 Quiz II 3/18/05 Your Name: _ TA's Name:...

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