Neurospora of genotype a + c are crossed withNeurospora of genotype + b +. (Here, + is shorthandfor the wild-type allele.) The following tetrads areobtained (note that the genotype of the four sporepairs in an ascus are listed, rather than listing alleight spores):a + c a b c + + c + b c a b + a + ca + c a b c a + c a b c a b + a b c+ b + + + + + b + + + + + + c + + ++ b + + + + a b + a + + + + c + b +137 141 26 25 2 3a. In how many cells has meiosis occurred to yieldthese data?b. Give the best genetic map to explain these results.Indicate all relevant genetic distances, both betweengenes and between each gene and the centromere.c. Diagram a meiosis that could give rise to oneof the three tetrads in the class at the far right inthe list

Neurospora of genotype a + c are crossed withNeurospora of genotype + b +. (Here, + is shorthandfor the wild-type allele.) The following tetrads areobtained (note that the genotype of the four sporepairs in an ascus are listed, rather than listing alleight spores):a + c a b c + + c + b c a b + a + ca + c a b c a + c a b c a b + a b c+ b + + + + + b + + + + + + c + + ++ b + + + + a b + a + + + + c + b +137 141 26 25 2 3a. In how many cells has meiosis occurred to yieldthese data?b. Give the best genetic map to explain these results.Indicate all relevant genetic distances, both betweengenes and between each gene and the centromere.c. Diagram a meiosis that could give rise to oneof the three tetrads in the class at the far right inthe list

Name: Neurospora of genotype a + c are crossed withNeurospora of genotype +
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Description: Neurospora of genotype a + c are crossed withNeurospora of genotype + b +. (Here, + is shorthandfor the wild-type allele.) The following tetrads areobtained (note that the genotype of the four sporepairs in an ascus are listed, rather than listing al

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter6: Cytogenetics: Karyotypes And Chromosome Aberrations

Section: Chapter Questions

Problem 2QP: Given the karyotype shown at right, is this a male or a female? Normal or abnormal? What would the...

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From the fungal cross arg-6 ⋅ al-2 × arg-6+ ⋅ al-2+, whatwill the spore genotypes be in unordered tetrads thatare (a) parental ditypes? (b) tetratypes? (c) nonparental ditypes?
The a, b, and c loci are all on different chromosomesin yeast. When a b+ yeast were crossed to a+ b yeastand the resultant tetrads analyzed, it was found thatthe number of nonparental ditype tetrads was equal tothe number of parental ditypes, but there were no tetratype asci at all. On the other hand, many tetratypeasci were seen in the tetrads formed after a c+ wascrossed with a+ c, and after b c+ was crossed withb+ c. Explain these results.
A Neurospora cross was made between a strain that carried the mating-type allele A and the mutant allele arg-1and another strain that carried the mating-type allele aand the wild-type allele for arg-1 (+). Four hundred linear octads were isolated, and they fell into the sevenclasses given in the table below. (For simplicity, they areshown as tetrads.)a. Deduce the linkage arrangement of the mating-typelocus and the arg-1 locus. Include the centromere orcentromeres on any map that you draw. Label all intervalsin map units.b. Diagram the meiotic divisions that led to class 6. Labelclearly
The life cycle of the haploid fungus Ascobolus is similar tothat of Neurospora. A mutational treatment producedtwo mutant strains, 1 and 2, both of which when crossedwith wild type gave unordered tetrads, all of the followingtype (fawn is a light brown color; normally, crosses produce all black ascospores):spore pair 1 black spore pair 3 fawnspore pair 2 black spore pair 4 fawna. What does this result show? Explain.The two mutant strains were crossed. Most of the unordered tetrads were of the following type:spore pair 1 fawn spore pair 3 fawnspore pair 2 fawn spore pair 4 fawnb. What does this result suggest? Explain.When large numbers of unordered tetrads were screenedunder the microscope, some rare ones that containedblack spores were found. Four cases are shown here:Case A Case B Case C Case Dspore pair 1 black black black blackspore pair 2 black fawn black abortspore pair 3 fawn fawn abort fawnspore pair 4 fawn fawn abort fawn(Note: Ascospores with extra genetic material…
An individual heterozygous for a reciprocal translocation possesses the following chromosomes: A B • C D E F G A B • C D V W X R S • T U E F G R S • T U V W X Q. Give the products that result from alternate, adjacent-1, and adjacent-2 segregation.
On Neurospora chromosome 4, the leu3 gene is just to theleft of the centromere and always segregates at the firstdivision, whereas the cys2 gene is to the right of the centromere and shows a second-division segregation frequency of 16 percent. In a cross between a leu3 strain anda cys2 strain, calculate the predicted frequencies of thefollowing seven classes of linear tetrads where l = leu3 andc = cys2. (Ignore double and other multiple crossovers.)
Based on your knowledge of genetics, how would you determine whether kanamycin or BASTA-resistant T2 seedlings are homo- or hemizygous for Bar or NPTII?
From a series of two-point crosses, the following mapdistances were obtained for the syntenic genes A, B,C, and D in peas:B ↔ C 23 m.u.A ↔ C 15 m.u.C ↔ D 14 m.u.A ↔ B 12 m.u.B ↔ D 11 m.u.A ↔ D 1 m.u.Chi-square analysis cannot reject the null hypothesis of no linkage for gene E with any of theother four genes.a. Draw a cross scheme that would allow you todetermine the B ↔ C map distance.b. Diagram the best genetic map that can be assembled from this data set.c. Explain any inconsistencies or unknown features inyour map.d. What additional experiments would allow you toresolve these inconsistencies or ambiguities?
During ascus formation in Neurospora, any ascosporewith a chromosomal deletion dies and appears whitein color. How many of the eight ascospores in theascus would be white if the octad came from a crossof a wild-type strain with a strain of the oppositemating type carrying:a. a paracentric inversion, and no crossovers occurredbetween normal and inverted chromosomes?b. a pericentric inversion, and a single crossoveroccurred in the inversion loop?c. a paracentric inversion, and a single crossoveroccurred outside the inversion loop?d. a reciprocal translocation, and an adjacent-1segregation occurred with no crossovers betweentranslocated chromosomes?e. a reciprocal translocation, and alternate segregationoccurred with no crossovers between translocatedchromosomes?f. a reciprocal translocation, and alternate segregation occurred with one crossover between translocated chromosomes (but not between thetranslocation breakpoint and the centromereof any chromosome)?
Homozygous wild-type male mice (AA BB CC) were crossed with triplemutant female mice (aa bb cc), forming an F1 generation with the followinggenotype (Aa Bb Cc). The F1 males were crossed with triple mutantfemales, forming the following F2 phenotypes”“a B c” 3“A b C” 3“a b c” 8“A B c” 5“a b C” 5“A B C” 8“a B C” 6“A b c” 6 44 Determine the sequence of the genes
. Imagine that you have done a cross between twostrains of yeast, one of which has the genotype A B Cand the other a b c, where the letters refer to threerather closely linked genes in the order given. Youexamine many tetrads resulting from this cross, andyou find two that do not contain the expected two Band two b spores. In tetrad I, the spores are A B C, AB C, a B c, and a b c. In tetrad II, the spores are A BC, A b c, a b C, and a b c. How have these unusualtetrads arisen?
From parents of genotypes A/A ⋅ B/B and a/a ⋅ b/b, adihybrid was produced. In a testcross of the dihybrid,the following seven progeny were obtained:A/a ⋅ B/b, a/a ⋅ b/b, A/a ⋅ B/b, A/a ⋅ b/b,a/a ⋅ b/b, A/a ⋅ B/b, and a/a ⋅ B/bDo these results provide convincing evidence of linkage?