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Unformatted text preview: PHYS521. Biological Physics. Midterm Exam #1 October 7, 2010 Each problem is graded out of 10 points. It is enough to solve two problems to get full credit for the exam. If you solve more problems, you will have extra credit. Please give understandable explanations. No partial credit will be given for wrong results without explanations. Problem 1 Suppose that you purify a viral DNA sample consisting of doublestranded DNA molecules of length 50000 base pairs suspended in salt solution. Using light scattering, you find that each molecule is a blob of diameter 2 m. Your lab partner prepares a DNA sample, in the same buffer solution, from some other organism; her DNA molecules are hundred times longer. How big are the blobs in her sample? Solution: The size of the blob is proportional to a square root of N , the number of monomers. If N is increased 100 times without changing any other conditions, the size of the blob increases 10 times. The answer is 20 m....
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 Fall '10
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 Physics

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