BIO-366-Key-Test 1-Sep8-2009

BIO-366-Key-Test 1-Sep8-2009 - NAME: UTEID: BIO-366; Test...

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NAME : UTEID : BIO-366; Test 1. September 7, 2009 (Tuesday) 11.00 am to 12.10 pm. Please provide brief answers. Try to attempt all problems or as many as you can. Don’t get stuck on any one problem. Answer first those that you are most comfortable with. Then return to the ones that are more difficult for you. A. 1 . In the classical paper by Watson and Crick on the structure of the DNA, what was the most significant biological insight that the complementarity of the base pairs provided? Answer: The structure provided a mechanism for copying genetic information faithfully. The base pairing rule of A-T and G-C would produce two DNA molecules of the same sequence as the parent molecule. 2. The analysis by the chemist Chargaff helped Watson and Crick derive the base complementarity rule. What did this analysis find? Answer: Chargaff’s analysis of DNA from different sources showed that the molar percentage of A matched that of T, and the molar percentage of G matched that of C. This rule held even when the total GC to AT ratio varied significantly among the DNA samples. 3. What chemical force is responsible for complementary pairing of the bases in DNA? How many of these bonds are there between A and T? How many between C and G? Answer: Hydrogen bonding between A and T, G and C. The A-T base pair has two hydrogen bonds, the G-C base pair has three hydrogen bonds. 4. What is the nature of the chemical linkage in the sugar-phosphate backbone polymer of DNA? Answer: The bond between the phosphate group and the adjacent deoxyribose units is a phosphodiester bond 1
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5. Which carbon atoms of adjacent deoxyribose units are involved in linking the two? Answer: The 5’ carbon of one ribose unit is linked to the 3’ carbon of the adjacent one via a phosphodiester bond. 6. How many base pairs are there per turn of DNA in A-form DNA? Is the number larger or smaller than in B form DNA? Answer: There are 10.7 (close to 11) bp per turn in A form DNA. The number is large than in B form, which is 10.5. 7. Is the diameter of Z-form DNA smaller or larger than B-form DNA? What is the handedness of the backbone of the Z-helix? Answer: The diameter of Z-form DNA is smaller than that of B form. The
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This note was uploaded on 02/21/2010 for the course BIO 45 taught by Professor Sadasivan during the Spring '08 term at University of Texas at Austin.

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BIO-366-Key-Test 1-Sep8-2009 - NAME: UTEID: BIO-366; Test...

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