midterm1

midterm1 - CHEM114C Midterm I April 24, 2008 Name _ ID#_...

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CHEM114C Name ______________________________ Midterm I -1- April 24, 2008 ID#________________________________ Please write your name on each page. Your exam should have 6 pages including this cover page, with a total of 5 questions. Be certain that all work you want graded is written in permanent ink. You can use the back of the page to continue your answer. Do not use a calculator. This exam is 60 min long – work swiftly, most answers are short. GOOD LUCK! Your score 1. (30)_________ 2. (30)_________ 3. (30)_________ 4. (25)_________ 5. (25)_________ Total (140)______________
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CHEM114C Name ______________________________ Midterm I -2- 1. Some DNA questions (30) 1.1. Draw a G-C base-pair showing carbons, hydrogen bonds, and where the sugar is attached (5). a simple drawing as in Fig. 23.1 1.2. Summarize the differences between A-, B- and Z- DNA in the table below (12) A DNA B DNA Z DNA helical sense right right left diameter 26A, 2.6nm 20A, 2nm 18A, 1.8nm no. of bases per turn 11.6 10 or 10.4 12 relative size of major groove narrow and deep wide and deep flat 1.3. B-form DNA is the most prevalent in vivo. What is the evidence that the Z-form may exist, too? (2) A DNA binding protein was found that binds Z-DNA specifically. What double stranded nucleic acid is found in an A-form helix in nature? (2) the RNA-DNA hybrid 1.4. Showing your work on the back of this page (calculator not required), calculate the length (to 2 significant figures) of a) 1,000,000 bp of B-DNA? (3) 1,000,000 x .34 nm = 340,000 nm = 340 μm (take a point off when not converted to μm) b) after this DNA has been packaged into nucleosomes to form a 11nm fiber (3) compaction ratio is 7: 340μm / 7 = about 50 μm c) when the nucleosomal DNA forms a 30nm fiber (3) compaction ration is 5: 50μm / 5 = 10 μm.
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CHEM114C Name ______________________________ Midterm I -3- 2. DNA replication (30) 2.1. Describe the experiment performed by Meselson and Stahl in 1958 to determine that DNA replication is semi-conservative. Describe the experimental techniques and
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midterm1 - CHEM114C Midterm I April 24, 2008 Name _ ID#_...

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