Prelim 2.key - 1. DNA sequencing (16 points) The following...

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1. DNA sequencing (16 points) The following DNA fragment was sequenced by the Sanger method. The asterisk indicates a fluorescent label. 5’ _______ 3’-OH 3’ _______ATCCGATTACAG----------5’ A sample of the DNA was reacted with DNA polymerase and each of the nucleotide mixtures (in an appropriate buffer) listed below. Dideoxynucleotides (ddNTPs) were added in relatively small amounts. 1. All 4 dNTPs and all 4 ddNTPs (creates a ladder as a control) (1 pt) 2. dATP, dCTP, dGTP, dTTP, ddCTP (3 pts) 3. dATP, dTTP, dGTP (3 pts) 4. dCTP, dTTP, dGTP, ddATP (3 pts) 5. dATP, dCTP, dGTP, dTTP, ddTTP, ddGTP (3 pts) The resulting DNA was separated by electrophoresis on an agarose gel, and the fluorescent bands on the gel were located. What would each of the lanes of the gel look like? Assuming that you had no information about the template sequence, based on what you observed on the gel, deduce the putative nucleotide sequence by writing the sequence along the right side of the gel. Indicate ambiguities where appropriate (such as A/T, A or T) (3 pts) Lane 1 lane 2 lane 3 lane 4 lane 5 1 large small CTG TAA TCG GAT C G/T G/T G/T A A G/T C G/T G/T A G/T
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2. DNA topology (16 points) (2 pts for each answer) Describe the general biochemical activity of a topoisomerase. It is a nicking-closing enzyme that changes the topology of circular DNA molecules by cleaving and ligating DNA strands resulting in a change of the linking number. Describe the role of topoisomerase in two biological processes OTHER THAN relaxing positive supercoils at the DNA replication fork. a. Condensation of chromosome in M phase by introducing positive supercoils in concert with condensing or packaging of chromosomes. b. Decondensation of chromosome in G1 phase by introducing negative supercoils in concert with histone spools. c.
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This note was uploaded on 12/20/2011 for the course BIOLOGICAL 3310 taught by Professor Goldburg during the Spring '10 term at Cornell.

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Prelim 2.key - 1. DNA sequencing (16 points) The following...

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