Exam 3 Fall 07 key - NAME: _ EID:_ Bio325 Exam III November...

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NAME: __________________ EID:_____________________ Bio325 Exam III November 15, 2007
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1) . The biochemical pathway shown below details the production of histidine from the precursors M1 and X2 by four essential enzymes, 1, 2, 3, and 4 in budding yeast. The compounds A3, G5, and C1 are intermediates in this process. Note that enzyme 3 combines A3 and G5 to make the intermediate C1. 1 3 a. (7 pts) You have several haploid strains of budding yeast, each of which has a mutation in a single gene encoding one of the enzymes. The chart below summarizes whether each mutant grows when supplemented with the compounds A3, C1, G5, M1, X2 or histidine. Based on the diagram above, fill in the chart with “-” for no growth or “+” for growth. supplements: Strain: - A3 C1 G5 M1 X2 histidine Wild-type + + + + + + + Mutant 1 - + + - - - + Mutant 2 - - + + - - + Mutant 3 - - + - - - + Mutant 4 - - - - - - + b. (3 pts) If mutant 2 and mutant 3 were mated to make a diploid strain, what would be the phenotype of the resulting strain (i.e. would it be a histidine auxotroph or prototroph)? c. (3 pts) If the diploid in b was self-crossed to make an F 2 generation of diploids, what would be the ratios of phenotypes (assume that the genes are not linked)? d. (3 pts) what intermediate(s) would accumulate in a 3 - 3 - 4 - 4 - double homozyous mutant? M1 A3 C1 histidine G5 2 4 X2 histidine prototroph 9:7 his+ :his- A3 and G5
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2) Mutations at the T locus in mice can result in liver dysfunction in the mouse. The T 1 allele is the wild-type allele and the T 2 allele is a mutant allele that has a nonsense mutation near the beginning of the gene. T 2 T 2 homozygotes have liver dysfunction. When a T 1 T 1 homozygote is crossed with a T 2 T 2 homozygote, the resulting heterozygous mice also have liver dysfunction. a. (3 pts) Based on this data, is the T 2 allele recessive or dominant to the T 1 allele ? b. (3 pts) What is the most likely reason for this? (Either write the name for this phenomenon or describe the molecular basis) 3) a. (2 pts) What part of a gene is most important in regulating the initiation of transcription? b. (2 pts) What is the product of transcription? c. (2 pts) A transcription termination signal is recognized in the form of (circle one): 1. DNA 2. RNA 3. a DNA/RNA hybrid 4. none of the above d. (2 pts) To the right is a picture of a DNA/RNA hybrid. If this was an intermediate structure formed during transcription, what atom would be the nucleophile for the next polymerization event? (Circle the atom) dominant haploinsufficiency the promoter RNA
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4) Shown below is a DNA molecule that will be transcribed, with the template and non-template
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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Exam 3 Fall 07 key - NAME: _ EID:_ Bio325 Exam III November...

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