Introduction to Genetic Analysis
11th Edition
ISBN: 9781464109485
Author: Anthony J.F. Griffiths, Susan R. Wessler, Sean B. Carroll, John Doebley
Publisher: W. H. Freeman
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Chapter 4, Problem 38.2P
Summary Introduction
To determine: The number of ascospores in the ascus of Neurospora.
Introduction. The genotype is the genetic constitution of the organism while the
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The following results are derived from crosses between Neurospora strain xy and strain ++:
Tetrad Class
3
4
ху
x+
x+
xy
++
++
++
+y
+y
ху
+y
25
++
3
124
4
(i)
Name the ascus type of each class from 1 to 4 as P, NP or T.
(ii)
Are genes x and y linked? Explain your answer.
(iii)
If they are linked, determine the map distance between the two genes. If they are
unlinked, provide all the information you can about why you draw this conclusion.
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
Please label the tetrad type in the table as PD (parental ditype), NPD (non parental ditype) or T (tetratype) and answer the following questions
a) Are the genes linked? Please explain SPECIFICALLY how you can distinguish between linked and unlinked genes in this instance.
b) If the two genes are linked, calculate the % recombination between ser and thr. Show the formula used, as well as all of your calculations.
c) Draw a single map illustrating the arrangement of the two genes on the chromosome with respect to each other and to the centromere of the chromosome. Make sure to map ALL three distances
Chapter 4 Solutions
Introduction to Genetic Analysis
Ch. 4 - Prob. 1PCh. 4 - Prob. 5PCh. 4 - Prob. 12PCh. 4 - Prob. 13PCh. 4 - Prob. 14PCh. 4 - Prob. 15PCh. 4 - Prob. 16PCh. 4 - Prob. 17PCh. 4 - Prob. 18PCh. 4 - Prob. 19P
Ch. 4 - Prob. 20PCh. 4 - Prob. 21PCh. 4 - Prob. 21.1PCh. 4 - Prob. 21.2PCh. 4 - Prob. 21.3PCh. 4 - Prob. 21.4PCh. 4 - Prob. 21.5PCh. 4 - Prob. 21.6PCh. 4 - Prob. 21.7PCh. 4 - Prob. 21.8PCh. 4 - Prob. 21.9PCh. 4 - Prob. 21.10PCh. 4 - Prob. 21.11PCh. 4 - Prob. 21.12PCh. 4 - Prob. 21.13PCh. 4 - Prob. 21.14PCh. 4 - Prob. 21.15PCh. 4 - Prob. 21.16PCh. 4 - Prob. 21.17PCh. 4 - Prob. 21.18PCh. 4 - Prob. 21.19PCh. 4 - Prob. 21.20PCh. 4 - Prob. 21.21PCh. 4 - Prob. 21.22PCh. 4 - Prob. 21.23PCh. 4 - Prob. 21.24PCh. 4 - Prob. 21.25PCh. 4 - Prob. 21.26PCh. 4 - Prob. 22PCh. 4 - Prob. 23PCh. 4 - Prob. 24PCh. 4 - Prob. 25PCh. 4 - Prob. 26PCh. 4 - Prob. 27PCh. 4 - Prob. 28PCh. 4 - Prob. 29PCh. 4 - Prob. 30PCh. 4 - Prob. 31PCh. 4 - Prob. 32PCh. 4 - Prob. 33PCh. 4 - Prob. 34PCh. 4 - Prob. 35PCh. 4 - Prob. 36PCh. 4 - Prob. 37PCh. 4 - Prob. 38PCh. 4 - Prob. 38.1PCh. 4 - Prob. 38.2PCh. 4 - Prob. 38.3PCh. 4 - Prob. 38.4PCh. 4 - Prob. 38.5PCh. 4 - Prob. 38.6PCh. 4 - Prob. 38.7PCh. 4 - Prob. 38.8PCh. 4 - Prob. 38.9PCh. 4 - Prob. 38.10PCh. 4 - Prob. 38.11PCh. 4 - Prob. 38.12PCh. 4 - Prob. 38.13PCh. 4 - Prob. 38.14PCh. 4 - Prob. 38.15PCh. 4 - Prob. 38.16PCh. 4 - Prob. 38.17PCh. 4 - Prob. 38.18PCh. 4 - Prob. 38.19PCh. 4 - Prob. 38.20PCh. 4 - Prob. 38.21PCh. 4 - Prob. 38.22PCh. 4 - Prob. 38.23PCh. 4 - Prob. 38.24PCh. 4 - Prob. 39PCh. 4 - Prob. 40PCh. 4 - Prob. 41PCh. 4 - Prob. 42PCh. 4 - Prob. 43PCh. 4 - Prob. 44PCh. 4 - Prob. 45PCh. 4 - Prob. 46PCh. 4 - Prob. 47PCh. 4 - Prob. 48PCh. 4 - Prob. 49PCh. 4 - Prob. 50PCh. 4 - Prob. 51PCh. 4 - Prob. 52PCh. 4 - Prob. 53PCh. 4 - Prob. 54PCh. 4 - Prob. 55PCh. 4 - Prob. 56PCh. 4 - Prob. 57PCh. 4 - Prob. 58PCh. 4 - Prob. 59PCh. 4 - Prob. 60PCh. 4 - Prob. 62PCh. 4 - Prob. 63PCh. 4 - Prob. 64PCh. 4 - Prob. 65PCh. 4 - Prob. 66PCh. 4 - Prob. 67PCh. 4 - Prob. 68PCh. 4 - Prob. 69P
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- his-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_forwardA 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 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_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_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_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
- One yeast strain carries the alleles lys+ and arg+, whereas another strain has lys-3 and arg-2. The two strains were crossed toeach other, and an ascus obtained from this cross has four spores with the following genotypes: lys+ arg+, lys+ arg-2, lys-3arg+, and lys-3 arg 2. This ascus has a. a parental ditype.b. a tetratype.c. a nonparental ditype.d. either a tetratype or a nonparental ditype.arrow_forwardAlleles 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 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
- The 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_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 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_forward
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