ANSWERS TO Exam Questions from Exam 3 – Eukaryotic Gene Regulation, GenomeModifications in Eukaryotes, Population Genetics1. Consider an autosomal recessive trait that occurs at a frequency of 10-6 in aspecific human population that is at Hardy-Weinberg equilibrium (ie. random mating isoccurring).(a)(b) 85%(c) decrease(d) all three of these choices could act to keep q constant2. You are studying regulation of the Wrm1 gene, a yeast gene that is expressed inresponse to heat.(a) constitutive(b) recessive(c) trans(d) dominant negative activator(e)Tetrad Type ANumber of these tetrads out of a total of 90: _________86_______Classification of these tetrads (PD, NPD, or TT): ______PD________Color in the spores that would be blue in color when growing on the following plates:X-gal, 24°C X-gal, 36°CTetrad Type BNumber of these tetrads out of a total of 90: ________4________Classification of these tetrads (PD, NPD, or TT): ________TT_________Color in the spores that would be blue in color when growing on the following plates: X-gal, 24°C X-gal, 36°C3. The scenario in this question asks a biological question that can be addressed bycreating genetically engineered mice. i) pronuclear injection ii) the d-Nhe gene iii) fertilized egg iv) NheJ+/NheJ– v) randomly vi) no vii) you would have to cross two of the transgenic mice you made and screen formice that are NheJ– / NheJ– / d-NheJ viii) if these mice are UV sensitive, then the two genes are not interchangeable; ifthese mice are UV sensitive, then the two are interchangeableNOTE that the two plates arereplicas, so the top spore onthe left plate has the samegenotype as the top spore onthe right plate.4. You are studying how yeast cells grow on the sugar maltose as a carbon source.(a)A: negative regulator, maltoseB: positive regulator, maltoseC: negative regulator, glucose(b) constitutive(c)maltose B --] A glucose C(d) Region 2(e) Deletions 4 and 55. You have a mutant mouse that displays the phenotype of white fur (instead of thewild-type color for this strain, which is brown fur).1. gene targeting2. the allele of whfr that is found in the mutant mouse3. ES cells4. wild-type5. The whfr locus6. Mate the chimeric heterozygote that results to wild-type to get a non-chimericheterozygote. Then mate two non-chimeric heterozygotes together, and 1/4 of theirprogeny will be the mouse you want.7. if the mouse has white fur, then the whfr mutation itself is sufficient to causethe white fur phenotype. If the mouse is brown, then a combination of mutations musthave caused the white mutant mouse to be white.6. An allele that causes the recessive phenotype of microcephaly has a frequency q =0.0001 in a randomly-mating population in Hardy-Weinberg equilibrium.(a) frequency = 10-8(b) h = 0.00009(c) q = 0.0000447maltase7. You are studying a yeast strain that will grow using the sugar raffinose as acarbon source.(a) the mutations both give recessive phenotypes and are in different genes(b) uninducible(c) raffinose --] 2 --] 3 Raf1(d) you would get all PDs, which would each have two uninducible spores and twoconstitutive spores8. Suppose that, in an isolated population, there exists a very rare inherited anemiawhich is autosomal recessive.(a) q2(b) 2pq, which approximately equals 2q(c) (1/16)(d) 0.008Fq = 0.001q(e) 0.008 Fq = q2so q = 0.0019. You are studying the sihZ gene in mice, and you isolate a mutation called “regX”that disrupts proper transcriptional regulation of the sihZ gene.(a) pronuclear injection(b) insert the regX mutant allele distal from the sihZ gene(c) use the regX allele from the regX mutant animal. Do not put the sihZ open readingframe on this fragment. This fragment will integrate randomly.(d) fertilized egg, wild-type animal(e) no additional breeding(f) If the sihZ gene is properly regulated in the transgenic animal, then the elementworks in cis and is a regulatory DNA region upstream of the sihZ gene. If the sihZ geneis improperly regulated in the transgenic animal, then the element works in trans andencodes a regulatory protein.10. A early nonsense mutation in the yeast URA9 gene gives an intermediate levelof growth without the nucleotide uracil being provided in the growth medium (Ura+/–).(a) You have isolated a suppressor mutation that is unlinked to the original mutation.This suppressor mutation alone gives a Ura+ phenotype. The suppressor may be in atRNA gene, causing a nonsense-suppressing allele of this tRNA gene.(b) You have isolated a synthetic mutation that is unlinked to the original mutation. Thissynthetic mutation alone gives a Ura+/- phenotype. The synthetic mutation may be inanother gene that is partially necessary for synthesis of the nucleotide uracil, such that,without the function of this gene, the cell is Ura+/-, but without the function of this geneand without the function of Ura9, the cell is fully Ura-.(c) The suppressor mutation and the synthetic mutation are tightly linked.(d) The tRNA suppressor mutation must also suppress the mutation will isolated inpart (b). Thus the synthetic mutation (which on it’s own gives a Ura+/- phenotype) alsomust be a nonsense mutation of the same category (opal, ochre, amber) as youroriginal mutation. This allows a triple mutant strain (with the original mutation, thesynthetic mutation, and the suppressor mutation) to have a Ura+ phenotype.11. Trekking in the Himalayas, you discover a “founder generation” of 1000 goatsbarricaded on all sides by high peaks and massive glaciers.(a) f(A) = 0.3 and f(a) = 0.7(b) no(c) f(A) = 0.3(d) f(AA) = 0.09 and f(Aa) = 0.42 and f(aa) = 0.4912. The scenario in this question asks a biological question that can be addressedby creating genetically engineered mice. i) pronuclear injection ii) the PrfM gene from the mouse that can smell perfume iii) fertilized egg iv) a homozygous knockout of PrfM v) randomly vi) no vii) none viii) If you ever generate a mouse that can smell, then the mutation was intragenic.If you never get a mouse that can smell, then the mutation was extragenic.13. You are studying the regulation of Gln1, a yeast gene involved in glutaminesynthesis.(a) constitutive(b) yes, at 37cM(c) ten of those 17 spores(d) glutamine –] 8 --] 7 --] 114. Albinism is a rare
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