Concept explainers
a.
To determine: The linkage arrangement of of mating type locus and arg-1 locus.
Introduction: Meiosis, also known as the reductional division, is the second type of cell division that takes place in eukaryotes. The cell division is marked by a decrease in the chromosome number to half. This type of cell division allows the recombination of the genes on the chromosome to produce a zygote.
b.
To determine: The meiotic divisons leading of class 6 of the progeny class.
Introduction: The genes are the sequence of
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Introduction to Genetic Analysis
- A yeast geneticist irradiates haploid cells of a strain thatis an adenine-requiring auxotrophic mutant, caused bymutation of the gene ade1. Millions of the irradiatedcells are plated on minimal medium, and a small number of cells divide and produce prototrophic colonies.These colonies are crossed individually with a wildtype strain. Two types of results are obtained:(1) prototroph × wild type : progeny all prototrophic(2) prototroph × wild type : progeny 75% prototrophic,25% adenine-requiring auxotrophsa. Explain the difference between these two types ofresults.b. Write the genotypes of the prototrophs in each case.c. What progeny phenotypes and ratios do you predictfrom crossing a prototroph of type 2 by the original ade1auxotroph?arrow_forwardA yeast geneticist irradiates haploid cells of a strain that is an adenine-requiring auxotrophic mutant, caused by mutation of the gene ade1. Millions of the irradiated cells are plated on minimal medium, and a small number of cells divide and produce prototrophic colonies. These colonies are crossed individually with a wildtype strain. Two types of results are obtained:(1) prototroph × wild type : progeny all prototrophic(2) prototroph × wild type : progeny 75% prototrophic, 25% adenine-requiring auxotrophsa. Explain the difference between these two types of results.b. Write the genotypes of the prototrophs in each case.c. What progeny phenotypes and ratios do you predict from crossing a prototroph of type 2 by the original ade1auxotroph?arrow_forwardhis-l and lys-3 are alleles found in baker's yeast that require histidine and lysine for growth, respectively. A cross was made between two haploid yeasts that are his-1 lys-3 and his lys". From the analysis of 900 individual tetrads, the following numbers of tetrads were obtained: GI: 2 spores are his-1 lys* +2 spores are his* lys-3 = 8 G2: 2 spores are his-1 lys-3+ 2 spores are his* lys* = 512 G3: 1 spore is his-1 lys-3 +1 spore is his-1 lys + 1 spore is his lys-3+ 1 spore is his" lys = 380 (i) Name the ascus type of each group as P, NP or T. (ii) Are the genes linked? Explain your answer. (iii) If the genes are linked, calculate the distance between the genes.arrow_forward
- 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 listarrow_forwardFemales of wild-type Strain A and males of mutant Strain B, as well as females of mutant Strain B and males of wild-type Strain A, make reciprocal crosses. Explain why reciprocal crosses are needed in genetics experiments involving Drosophila fruit flies.arrow_forwardConsider three genes L, U, and W, for which the count of F2 phenotypes after a 3-point cross is as follows: Phenotype F2 count: L U w 19 L u W 1 l u W 21 L U W 33 l U W 274 l u w 41 l U w 2 L u w 259 Which of the following statements about genes L, U, and W are TRUE? (may be more than one correct ans) A. L, U, and W are each on a different chromosome B. Only U and L are on the same chromosome C. Only U and W are on the same chromosome D. Only W and L are on the same chromosome E. L, U, and W are all on the same chromosomearrow_forward
- A Neurospora colony at the edge of a plate seemed to be sparse (low density) in comparison with the other colonies on the plate. This colony was thought to be a possible mutant, and so it was removed and crossed with a wild type of the opposite mating type. From this cross, 100 ascospore progeny were obtained. None of the colonies from these ascospores was sparse, all appearing to be normal. What is the simplest explanation of this result? How would you test your explanation? (Note: Neurospora is haploid.)arrow_forwardThe wild-type (W) Abraxas moth has large spots on its wings, but the lacticolor (L) form of this species has very small spots. Crosses were made between strains differing in this character, with the following results:Provide a clear genetic explanation of the results in these two crosses, showing the genotypes of all individual moths.arrow_forwardThe alleles his-5 and lys-1, found in yeast, result in cells that require histidine and lysine for growth, respectively. A cross was made between two haploid yeast strains that are his-5 lys-1 and his+ lys+. 973 tetrads were analyzed, with the follow pattern: 7 tetrads with 2 his-5 lys+ spores and 2 his+ lys-1 spores 603 tetrads with 2 his-5 lys-1 spores and 2 his+ lys+ spores 363 tetrads with 1 his-5 lys-1 spore, 1 his-5 lys+ spore, 1 his+ lys-1 spores, and 1 his+ lys+ spore Compute the map distance between these two genes using the method that considered double crossovers and the one that does not. Which gives the higher value? Why? What is the frequency of single crossovers between these genes? Explain. Based on the frequency of single-crossovers, how many double crossovers would one expect? Is positive interference occurring?arrow_forward
- Alleles of genes A and B were analyzed in Neurospora according to the cross shown below. Ordered tetrads are summarized in each horizontal row with the number of tetrads in each category listed alongside. A) Analyze the data to determine the recombination frequency (RF) between A and B, along with any additional information that is available from this data. B) Draw a map of the chromosome or chromosomes with appropriate map distances. C) Use the Perkins formula to reanalyze any relationship between A and B.arrow_forwardThe alleles his-5 and lys-1, found in yeast, result in cells that require histidine and lysine for growth, respectively. A cross was made between two haploid yeast strains that are his-5 lys-1 and his+ lys+. 973 tetrads were analyzed, with the follow pattern: 7 tetrads with 2 his-5 lys+ spores and 2 his+ lys-1 spores 603 tetrads with 2 his-5 lys-1 spores and 2 his+ lys+ spores 363 tetrads with 1 his-5 lys-1 spore, 1 his-5 lys+ spore, 1 his+ lys-1 spores, and 1 his+ lys+ spore Compute the map distance between these two genes using the method that considered double crossovers and the one that does not. Show your work. Which give the higher value? Why? What is the frequency of single crossovers between these genes? Explain. Based on the frequency of single-crossovers, how many double crossovers would one expect? Is positive interference occurring?arrow_forwardThe alleles his-5 and lys-1, found in yeast, result in cells that require histidine and lysine for growth, respectively. A cross was made between two haploid yeast strains that are his-5 lys-1 and his+ lys+. 973 tetrads were analyzed, with the following pattern: 7 tetrads with 2 his-5 lys+ spores and 2 his+ lys-1 spores 603 tetrads with 2 his-5 lys-1 spores and 2 his+ lys+ spores 363 tetrads with 1 his-5 lys-1 spore, 1 his-5 lys+ spore, 1 his+ lys-1 spores, and 1 his+ lys+ spore Compute the map distance between these two genes using the method that considered double crossovers and the one that does not. Show your work. Which give the higher value? Why? What is the frequency of single crossovers between these genes? Explain. Based on the frequency of single-crossovers, how many double crossovers would one expect? Is positive interference occurring?arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning