lastyearfinal07

lastyearfinal07 - Last Name: _ First Name: _ Student #: _...

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Last Name: ___________________ First Name: _______________ Student #: ____________ Section Number: ___________ Biology 200 Final Exam - Dec. 12, 2007 1. (6 marks). Cells at the Anaphase A and Anaphase B stages of mitosis are treated with taxol and colchicine. Indicate for each type of drug what the effects of these drugs would be on both Anaphase A and Anaphase B and why. 3 marks each: effect and explanation Taxol: prevents disassembly of MTs Colchicine: prevents assembly of MTs Effect on Taxol Colchicine Anaphase A Chromosomes would not move or move along MTs. Kinetochore MT disassembly at the kinetochore does not occur. (2 marks) None (1 mark) Anaphase B None (1mark) Interpolar MTs would not elongate; new tubulin units would not assemble on the (+) ends of the overlapping interpolar MTs. (2 marks) 2. (5 marks). Which of the following changes in cell membranes are likely to be seen when a cell culture growing at 37 o C is transferred to 25 o C? Indicate Yes or No, and briefly explain each case. No marks will be given for just stating Yes or No. a) Initial decrease in membrane fluidity b) Gradual replacement of shorter fatty acids by longer fatty acids in membrane phospholipids c) Gradual replacement of stearate (18 carbons, saturated) by oleate (18 carbons, 1 double bond) in the membrane phospholipids d) Enhanced rate of synthesis of unsaturated fatty acids e) Loss of integral proteins from the membrane 1 mark each: a) Yes; membrane fluidity is temperature dependent and shift to lower growth temperature will decrease membrane fluidity. b) No; longer chain fatty acids decrease membrane fluidity. c) Yes; unsaturated fatty acids increase membrane fluidity. d) Yes; unsaturated fatty acids increase membrane fluidity.
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e) No; there is no effect of temperature change on protein content 3. (12 marks). The mutagen acridine works by inserting or deleting one or more nucleotides into or from a DNA sequence. In the following examples, each insertion is represented by a + and each deletion by a –. (A) (8 marks) Which mutations would most likely generate a mutant, and which would most likely be normal? Assume that insertions and deletions occur in exons. A. + B. + – C. – + – + D. + + + + + + A. (2 marks). An insertion of a single nucleotide would shift the triplet code (or open reading frame) by one and thus protein would be completely different past the point of the mutation. This type of mutation is called “frameshift” mutation and would most likely result in a mutant protein. B. (2 marks). A single nucleotide insertion followed by a single nucleotide deletion would alter the amino acid specified by that codon, but would not affect the amino acid sequence of the rest of the protein. The protein would most likely be normal. C. (2 marks).
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lastyearfinal07 - Last Name: _ First Name: _ Student #: _...

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