Chem271_S07_x2

Chem271_S07_x2 - Score for the page Chemistry 271, Section...

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Unformatted text preview: Score for the page Chemistry 271, Section 21xx Your Name: University of Maryland, College Park Your SID #: General Chemistry and Energetics Prof. Jason Kahn Exam II (100 points total) May 2, 2007 You have 53 minutes for this exam. Exams written in pencil or erasable ink will not be re-graded under any circumstances. Explanations should be concise and clear . I have given you more space than you should need. There is extra space on the last page if you need it. You will need a calculator for this exam. No other study aids or materials are permitted. Generous partial credit will be given, i.e. , if you dont know, guess. Many useful equations are given on page 9. Honor Pledge: At the end of the examination time , please write out the following sentence and sign it, or talk to me about it: I pledge on my honor that I have not given or received any unauthorized assistance on this examination. 1. DNA Thermodynamics (25 pts) The formation of the double-stranded DNA 20-mer oligonucleotide below from the separated single strands has been measured to proceed with H = 128 kcal/mole and S = 346 cal/moleK. Assume a total strand concentration of 3 M (1.5 M for each strand). 5-TATTAAGCGACCACACATAA ATAATTCGCTGGTGTGTATT-5 (a; 7 pts) What is the T m for this oligonucleotide? What is the value of G at the T m ? Chemistry 271, section 21xx Exam II, 5/2/07 2/9 Score for the page (b; 8 pts) Briefly explain why H and S are each negative for the hybridization reaction. (c; 6 pts) Briefly and qualitatively explain how the nearest-neighbor rules for prediction of DNA melting thermodynamics are analogous to the bond-energy approximation used to estimate H f for previously unknown organic compounds. Chemistry 271, section 21xx Exam II, 5/2/07 3/9 Score for the page (d; 4 pts) The DNA microarrays sold by Affymetrix typically use 25-mer DNA probes. One application is to detect the amount of a known mRNA sequence in a clinical sample. Each target mRNA (or fluorescently labeled copy of same) typically hybridizes to 20 or so different probe oligonucleotides...
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This note was uploaded on 09/07/2011 for the course CHEM 271 taught by Professor Staff during the Spring '08 term at Maryland.

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Chem271_S07_x2 - Score for the page Chemistry 271, Section...

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