Name: __________________________17.03 Exam Three -- 2005Name: ______________________________Exam starts at 11:05 am and ends at 11:55 am.There are 8 pages including this cover page.Please write your name on each page.Only writing on the FRONT of every page will be graded.(You may use the backs, but only as scratch paper.)Question 1 17 pts________Question 2 45 pts________Question 3 20 pts________Question 4 18 pts________TOTAL out of 100_______Name: __________________________2 1. (17 pts) You are studying the expression of the yeast gene ProA that is necessaryfor the synthesis of the amino acid proline. ProA is normally expressed only when thecell is lacking supplemental proline in the growth medium. You isolate two haploidyeast strains (ProB– and ProC–) that misregulate ProA expression.You mate a ProB– haploid strain to a wild-type haploid strain. The resultingdiploid expresses ProA properly.You mate a ProB– haploid strain to a ProA– haploid strain. The resulting diploidexpresses ProA properly.You mate a ProA– ProC– haploid strain to a ProC– haploid strain. The resultingdiploid expresses ProA when proline is present in the growth medium.You mate a ProC– haploid strain to a ProA– haploid strain. The resulting diploidexpresses ProA properly.You mate a ProB– ProC– haploid strain to a wild-type haploid strain. Theresulting diploid expresses ProA properly. You induce sporulation of this diploid, andexamine 40 tetrads. 30 (of those 40) each contain: two spores that do not express ProAwhen proline is absent from the growth medium, one spore that expresses ProA whenproline is present in the growth medium, and one spore that expresses ProA properly.(a, 6pts) Classify the ProB– mutation by its genetic properties (cis vs. trans,constitutive vs. uninducible, dominant vs. recessive).(b, 6pts) Classify the ProC– mutation by its genetic properties (cis vs. trans,constitutive vs. uninducible, dominant vs. recessive).(c, 5pts) If you a drew a linear pathway showing the regulation of ProA, which functionwould you place closer to ProA: ProB or ProC?Name: __________________________32. (45 pts) You are studying the transcriptional regulation of a mouse gene calledStringy. This gene is normally only expressed in tail cells due to the presence of a tail-specific inducer molecule in these cells. You have isolated two true-breeding mutantstrains of mice that do not spatially regulate the expression of the Stringy gene properly.The strains of mice that you have, and their corresponding phenotypes, are listed in thetable below.Genotype of mouse Phenotype of mouseWild-type Stringy expressed only in tailA– / A–Stringy not expressed anywhereB– / B–Stringy expressed in all cells in the bodyWhen you cross mice that are B– / B– to mice that are deficient in Stringy, the resultingmice only have Stringy expressed in the tail.When you cross mice that are B– / B– to mice that are A– / A–, and then cross theresulting F1 mice to each other, you get a genotypic ratio in the F2 that indicates that theA and B loci segregate independently of each other.You inject a piece of DNA containing the A– allele of the A gene into a fertilized eggproduced by the mating of two true-breeding B– mice. You then transfer this injectedfertilized egg into a pseudopregnant mouse. The mouse that is born does not expressStringy in any cells in its body.(a, 6pts) Classify the A– mutation by its genetic properties (cis vs. trans, constitutivevs. uninducible, dominant vs. recessive).(b, 6pts) Classify the B– mutation by its genetic properties (cis vs. trans, constitutive vs.uninducible, dominant vs. recessive).Name: __________________________4(c, 12pts) Draw TWO different linear genetic pathways that are consistent with youranswers to parts (a) and (b). Be sure to indicate the wild-type A, B, and Stringy genesin your model, and also include the tail-specific inducer molecule.(d, 6pts) Clearly state which one piece of information you would need to know in orderto determine which of the models you drew in part (c) was correct.Name: __________________________5(e, 15pts) You want to distinguish between the two models listed in part (c). You coulddo this by creating a genetically engineered mouse. For the mouse you make, pleasestate: i) whether you are using pronuclear injection or gene targeting ii) what DNA you would introduce into the mouse cells (also draw the DNA) iii) what is the genotype of the fertilized egg or the ES cells you would start with iv) which additional breeding steps you would do to make the mouse you wanted v) two possible phenotypic results you could get from the newly made mice, and the corresponding conclusion you would make for each resultDescribe a way to create a genetically modified mouse that would allow you to gain thepiece of information you stated in part (d) (and thereby distinguish between yourmodels).i)ii)iii)iv)v)Name: __________________________63. (20 pts) For each situation below, predict whether the frequency of the ALLELE(“q”) associated with the trait/disorder in consideration will stay the same, rise, or fall.If you cannot conclude, choose “inconclusive.”For parts (a), (b) and (c), assume that the mutation rate is zero.(a, 5pts) There is a population in which a rare autosomal recessive trait (with S = 0, h =0) exists. This population always mates randomly. All of a sudden, heterozygotesobtain a selective advantage.The allele frequency “q” will: stay the same rise(CIRCLE ONE OF THE FOUR) inconclusive fall(b, 5pts) There is a population in which a rare autosomal recessive disorder (with S = 1,h = 0) exists. All of a sudden, this population goes from mating randomly toparticipating in some amount of inbreeding.The allele frequency “q” will: stay the same rise(CIRCLE ONE OF THE FOUR) inconclusive fall(c, 5pts) There is a population in which a rare autosomal dominant trait (with S = 0, h =0) exists. All of a sudden, this population goes from mating randomly to participating insome amount of inbreeding.The allele frequency “q” will: stay the same rise(CIRCLE ONE OF THE FOUR) inconclusive fall(d, 5pts) There is a population in which a rare autosomal recessive disorder (with S
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