7.03 Final Exam Name: TA: Alison Brauneis Tristan Kooistra Rishi Puram Sebastian Treusch Julie Valastyan Josh Wolf Section time: There are 15 pages including this cover page Please write your name on each page. Question 1 24 points Question 2 28 points Question 3 28 points Question 4 25 points Question 5 28 points Question 6 18 points Question 7 25 points Question 8 24 points2 Name: 1. You are studying the regulation of a new enzyme in E. coli, which is expressed only when an inducer compound is present. You have available an amber mutant in the structural gene for the enzyme, designated Enz—. You generate a collection of random Tn5 insertions in the E. coli chromosome and identify two insertions (called Tn5-1 and Tn5-2) that give constitutive expression of the enzyme. You carry out seperate P1 transduction experiments with each insertion mutant. In the first experiment you grow P1 phage on a Tn5-1 strain and use the resulting lysate to infect an Enz— mutant. All of the kanamycin resistant transductants express the enzyme constitutively. In the second experiment you grow P1 phage on a Tn5-2 strain and use the resulting lysate to infect an Enz— mutant. In this case, none of the kanamycin resistant transductants express the enzyme. (a 8 pts.) What can you conclude about each of the Tn5-1 and Tn5-2 mutations? Be as complete and specific as you can. (b 6 pts.) You obtain an F’ factor that contains the gene for the enzyme and surrounding region of the chromosome. When this F’ is mated into the Tn5-1 strain the resulting merodiploid expresses the enzyme constitutively, but when this F’ is mated into the Tn5-2 strain the resulting merodiploid exhibits normal regulation of the enzyme. What additional information do these experiments contribute to your understanding of the nature of either the Tn5-1 or Tn5-2 mutations.3 Name: (c 10 pts.) Diagram two different regulatory pathways that would explain the behavior of the Tn5-1 and Tn5-2 mutations. For your answer you will need to represent the wild type functions affected by the transposon mutations in the pathways (e.g. you may want to represent the gene affected by Tn5-1 as “Gene 1”). Also remember to include the inducer in both pathways. 2. Flies have a daily activity cycle showing peak activity in the morning and at night. To find genes that control this circadian rhythm, you seek mutant flies that are still active at a time when normal flies are inactive. To make your screen easier, you decide to look for recessive mutations on the X chromosome. (a 8 pts.) Depict an F1 screen that will allow you to find mutations on the X chromosome that recessively affect circadian rhythm.4 Name: Your first screen design proves highly challenging because of variability in circadian behavior from fly to fly. You therefore realize you need a screen design that allows you to assess the circadian behavior of a population of flies carrying a mutation. You mutagenize a male that carries a mutation in the X-linked white gene (w-, which recessively causes white eyes). You cross to a female that is heterozygous for a mutation, DTSa, which confers dominant temperature-sensitive lethality, and a balancer FM7a (DTSa/FM7a). FM7a confers a dominant “Bar” (eye shape) phenotype and recessive yellow body color (not recessive lethality). w-/Y male X DTSa/FM7a female (b 6 pts.) You raise the F1 at the non-permissive temperature (non-permissive for DTSa). Give the genotype and phenotype a viable F1 female carrying a hypothetical X-linked circadian mutation “m1”. (c 8 pts.) You cross individual F1 females to FM7a/Y males (one F1 female per cross in a vial). What will the genotypes and phenotypes of the F2 males and F2 females be? Depict the case for the cross involving the F1 female that carried m1. (d 6 pts.) If m1 confers a recessive defect in circadian behavior, which F2 flies in the vial will show abnormal behavior? If m1 confers a dominant defect, which flies will be affected?5 Name: 3. Americans have a wild type strain of yeast called strain 1. You take strain 1 and by mutagenesis collect a large number of mutations in that strain. These individual mutations are crossed to produce the quadruple mutant ade1 trp1 his1 lys1, which you call strain 2. You cross the original wild type strain 1 that has no growth requirements by the quadruple mutant strain 2 and dissect tetrads. Below are the tetrad types with the numbers of each type listed below. Strain 1 (American Wild Type) X Strain 2 (American ade1 trp1 his1 lys1) Growth on media lacking the indicated amino acid (a 8 pts.) Based on these data, draw a genetic map showing the relative order and map distances in cM for the four genes in the cross using the American strain. Indicate any ambiguities. His Trp Lys Ade + - + - His Trp Lys Ade + + - - + + - - + + - - + + - - + - + - + - + - + + - - His Trp Lys Ade + + - - + - + - + - + - + + - - His Trp Lys Ade + - + - - - + + - - + + + + - - 69 10 20 1 Spore 1 2 3 4 Spore 1 2 3 46 Name: The Europeans have their own wild type strain of yeast they call strain 3. Like the Americans they make lots of mutations and by the same procedures make a quadruple mutant ade1 trp1 his1 lys1, which they call strain 4. You cross the original wild type strain 3 that has no requirements by the quadruple mutant strain 4 and dissect tetrads. Below are the tetrad types with the numbers of each type below each. Strain 3 (European Wild Type) X Strain 4 (European ade1 trp1 his1 lys1) Growth on media lacking the indicated amino acid (b 8 pts.) Based on these data, draw a genetic map showing the relative order and map distances in cM for the four genes in the cross using the European strain. Indicate any ambiguities. His Trp Lys Ade + - + - His Trp Lys Ade + + - - + + - - + + - - + + - - + - + - + - + - + + - - His Trp Lys Ade + - + - + + - - + - + - + + - - His Trp Lys Ade - - + + + - + - - - + + + + - - 69 10 20 1 Spore 1 2 3 4 Spore 1 2 3 47 Name: (c 6 pts.) Diagram a genetic event that could
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