Practice questions for Exam 3- answer key corrected

Practice questions for Exam 3- answer key corrected - Exam...

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Exam III – Sample Practice Questions 1. The alkaline lysis procedure for purification of plasmid DNA uses three solutions: Solution 1: EDTA, RNAse, Glucose, Tris Solution 2: SDS, NaOH Solution 3: K Acetate What is the function of each of the listed components? Solution 1: EDTA – chelates divalent cations; Ca++ and Mg++ stabilize membranes and Mg++ co-factor for DNAse RNAse – degrades RNA Glucose – draws water from cell to help lysis Tris - buffer Solution 2: SDS – dissolves membranes, denatures protein NaOH – denatures DNA, denatures proteins, degrades RNA Solution 3: K Acetate – neutralizes pH; K-DS (potassium dodecyl sulfate) is insoluble ppt (SDS = Na-DS = sodium dodecyl sulfate is soluble) What happens to plasmid DNA, chromosomal DNA, RNA, and proteins at each of the steps? After adding soln 1: DNA, protein still in solution; RNA starts to be degraded After adding soln 2: plasmid DNA denatured but strands still linked; chromosomal DNA denatured; RNA hydrolyzed; protein denatured. All still in solution After adding soln 3: plasmid DNA renatures; get ppt of K-SDS which traps chromosomal DNA and the denatured protein (chr DNA can’t easily / completely renature because strands have become separated) Spin after soln 3: pellet has K-SDS with protein and chr DNA; supnt has plasmid DNA 2. You are given 6 cultures of DH5α each carrying a different
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Practice questions for Exam 3- answer key corrected - Exam...

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