exam 2 - BIOSC 0350 Spring Term 2084 Second Mid-Term Exam...

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BIOSC 0350 Name: ANSWER KEY Spring Term 2084 Second Mid-Term Exam Signature: March 6, 2008 Dr. Valerie Oke INSTRUCTIONS: 1. Print your name at the top of each page and make sure you have 11 exam pages, codon table, and one page of scrap paper. 2. Sign the first page of this examination in the space provided. 3. Take a few moments to look over the entire exam before answering any questions. Then, begin with the questions you are most comfortable answering. 4. Show your work. In some cases partial credit will be given. Write your final answers and work, including calculations if applicable, in the boxes or on the lines provided. 5. Please write legibly. Make your drawings clear. Be concise; you will not be given credit for extraneous information. 6. Some of the model systems described in this exam parallel actual genetic systems but are solely derived from the imagination of the instructors. 7. Remember to relax and do your best. Good Luck!! MAKE SURE TO LOOK AT THE WHOLE PROBLEM; IN MANY CASES PARTS DO NOT DEPEND ON EACH OTHER AND CAN BE DONE SEPARATELY! Print
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Name Page 2 of 11 BIOSC 0350 Mid-Term Exam 2 March 6, 2008 Question Possible Points Score 1 16 2 15 3 18 4 20 5 16 6 15 Total 100
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Name Page 3 of 11 BIOSC 0350 Mid-Term Exam 2 March 6, 2008 1) 16 points total. What’s wrong with this picture? The following diagram of DNA replication has four things that are either wrong or inaccurate. List what is wrong or inaccurate. Briefly describe what would be correct and why. You may make marks on the figure above if it helps you to explain. 1: 5’ and 3’ are reversed. DNA polymerase reads 3’ to 5’ and polymerizes 5’ to 3’. 2: Helicase is wrong. Helicase should be at the fork next to primase. 3: Enzyme where helicase is drawn should be topoisomerase. 4: DNA ligase is in the wrong position. It will act after DNA polymerase I degrades the primer and will, therefore, be acting at the 3’ end of the DNA region (see arrow in red). 5: No primer on leading strand (though usually not shown since would only be one right at the origin, which isn’t specified on the drawing). 6: DNA polymerase III is drawn inaccurately. It should be located at the fork for both the leading and lagging strand, with the lagging strand looped around.
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Name Page 4 of 11 BIOSC 0350 Mid-Term Exam 2 March 6, 2008 2) 15 points total. Three ara mutants of E. coli were induced by mutagen X. The ability of other mutagens to cause the reverse the change (ara ara + ) was tested, and the frequency of ara + cells among total cells after treatment is shown below: Mutagen tested Mutant None (control) 5-Bromouracil Hydroxylamine Proflavin ara1 1.5 × 10 8 5.0 × 10 5 1.8 × 10 8 1.6 × 10 8 ara2 2.0 × 10 7 2.0 × 10 4 3.0 × 10 5 1.9 × 10 7 ara3 6.0 × 10 7 1.1 × 10 5 1.5 × 10 5 5.9 × 10 7 5-bromouracil is almost identical to thymine, and pairs with adenine but in a transient state can
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exam 2 - BIOSC 0350 Spring Term 2084 Second Mid-Term Exam...

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