Exam Questions from Exam 3 – Eukaryotic Gene Regulation, Genome Modifications inEukaryotes, 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). When answering the following parts, show all of your calculations.(a) Draw a pedigree below that shows a mating between two relatives that wouldcorrespond to an inbreeding coefficient that equals 0.007813. Denote the matingbetween relatives with a double-bar connecting the two related parents. Start yourpedigree with the common pair of ancestors and end your pedigree with the two relatedparents who are mating.(b) Now say that all matings in Generation X of the given population are either betweenunrelated individuals, or have the same inbreeding coefficient as the mating describedin part (a). If the incidence of the trait in Generation “X+1” increases to a frequency of 2X10-6, what percentage of matings in Generation X must have been between unrelatedindividuals?(c) Now assume that this autosomal recessive trait causes lethality in childhood. If aconstant percentage of matings are between related parents for many generations,would you predict that q would increase OR decrease?(d) A constant percentage of matings has occurred between related parents for manygenerations, and yet you find experimentally that q has not changed. Of the threechoices below, circle ALL that could potentially act against the effect you chose inpart (c) in order to keep q constant. Explain in one sentence why you chose or did notchoose each option.Choice A: migrationChoice B: heterozygote advantage (Aa over AA)Choice C: mutation2. You are studying regulation of the Wrm1 gene, a yeast gene that is expressed inresponse to heat. You isolate a wrm1::lacZ strain that expresses β-galactosidase whenWrm1 is normally expressed (which is at 36°C but not at 24°C). You use thiswrm1::lacZ strain to perform a genetic screen looking for mutants that do not properlyregulate expression of Wrm1. In your screen, you isolate a series of mutant strains thateither show constitutive or uninducible expression of wrm1::lacZ.Your results indicate that the following is the correct pathway for regulation of Wrm1expression. Note that WrmY and WrmX are on the same chromosome, and that WrmX,WrmZ, and Wrm1 are all on different chromosomes. WrmY WrmX WrmZ Wrm1One of the mutant strains you isolate contains a mutation called WrmX–, which is in thecoding region of WrmX. You mate a WrmX– wrm1::lacZ haploid strain to a wrm1::lacZhaploid strain. The resulting diploids are white on X-gal plates that are incubated at24°C, and are blue on X-gal plates that are incubated at 36°C.(a) Classify the WrmX– mutation as constitutive OR uninducible.(b) Classify the WrmX– mutation as dominant OR recessive.(c) Classify the WrmX locus as cis-acting OR trans-acting with respect to Wrm1.You next isolate a mutant strain containing a mutation called WrmY–, which is in thecoding region of WrmY. You mate a WrmY– wrm1::lacZ haploid to a wrm1::lacZhaploid. The resulting diploids are white on X-gal plates, regardless of the temperatureat which the plates are incubated.(d) Classify WrmY– by the type(s) of mutation it could be with respect to Wrm1. (Yourchoices are: repressor –, activator –, UAS–, URS–, super activator, super repressor,dominant negative repressor, dominant negative activator.)heatYou create diploid yeast by mating WrmX– WrmY– wrm1::lacZ haploid yeast towrm1::lacZ haploid yeast. Sporulation of these diploids yields two types of tetrads, andyou correctly conclude (given the number of each type of tetrad) that the WrmX andWrmY loci are linked at a distance of 2.22 cM. (e) Depicted below are the two types of tetrads that resulted when you sporulated theabove diploids. For each type of tetrad, state how many you found of that tetrad (out ofa total of 90 tetrads), classify the tetrad as PD, NPD, or TT, and color in all of thespores that would be blue on each of the following Petri plates.Tetrad Type ANumber of these tetrads out of a total of 90: __________________Classification of these tetrads (PD, NPD, or TT): __________________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: __________________Classification of these tetrads (PD, NPD, or TT): __________________Color in the spores that would be blue in color when growing on the following plates: X-gal, 24°C X-gal, 36°CNOTE that the two plates arereplicas, so the top spore onthe left plate has the samegenotype as the top spore onthe right plate.3. The scenario in this question asks a biological question that can be addressed bycreating genetically engineered mice. When creating engineered mice, the following 8steps need to be considered. For the mouse you make, please state: i) whether you are using pronuclear injection or gene targeting techniques ii) what DNA you would introduce into the mouse cells (also draw the DNA) iii) whether you would put the DNA into a fertilized egg or ES cells iv) what is the genotype of the fertilized egg or the ES cells you would start with v) where in the mouse genome the DNA you introduced would integrate vi) whether creating the mouse should involve the generation of a chimera or not vii) which additional breeding steps you would do to make the mouse you wanted viii) two possible phenotypic results you could get from the newly made mice, and the corresponding conclusions you would make based on each result“Non-homologous end joining” is the process by which a DNA sequence gets insertedinto a chromosomal region to which it is not homologous. Having a functional copy ofthe gene “NheJ” is necessary for this process to occur in mice. A mouse with no copiesof the NheJ gene is sensitive to irradiation as an adult, but a heterozygote is notsensitive.You decide to test whether one copy of the Drosophila “d-Nhe” gene could fullycompensate for the absence of the mouse NheJ gene. You have wild-typehomozygous mice (NheJ+/NheJ+), heterozygous mice (NheJ+/NheJ–), andhomozygous mutant mice (NheJ–/NheJ–) readily available to you.4. You are studying how
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