4.15 The following classes and frequencies of ordered tetrads were obtained from the cross a* b* × a b in Neurospora. (Only one member of each pair of spores is shown.) What is the order of the genes in relation to the centromere? Spore pair Nser of asci 1-2 3-4 5-6 7-8 a* b+ at b+ ab a b 1766 a+ b+ a b at b+ ab 220 at b+ a b+ at b ab 14

4.15 The following classes and frequencies of ordered tetrads were obtained from the cross a* b* × a b in Neurospora. (Only one member of each pair of spores is shown.) What is the order of the genes in relation to the centromere? Spore pair Nser of asci 1-2 3-4 5-6 7-8 a* b+ at b+ ab a b 1766 a+ b+ a b at b+ ab 220 at b+ a b+ at b ab 14

Concepts of Biology

1st Edition

ISBN:9781938168116

Author:Samantha Fowler, Rebecca Roush, James Wise

Publisher:Samantha Fowler, Rebecca Roush, James Wise

Chapter8: Patterns Of Inheritance

Section: Chapter Questions

Problem 2ACQ: Figure 8.10 In pea plants, purple flowers (P) are dominant to white (p), and yellow peas (Y) are...

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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 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…
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.
On chromosome 4 in Nuerospora, the allele pyr-1 results in a pyrimidine requirement for growth. A cross is made between a pyr-1 and pyr+ strain and the following results were obtained: 26 of a 2:4:2 pattern of pyr-1:pyr+:pyr-1 25 of a 2:4:2 pattern of pyr+:pyr-1:pyr+ 24 of a 2:2:2:2 pattern of pyr-1:pyr+:pyr-1:pyr+ 457 of a 4:4 pattern of pyr-1:pyr+ 27 of a 2:2:2:2 pattern of pyr+:pyr-1:pyr+:pyr-1 452 of a 4:4 pattern of pyr+:pyr-1 What is the distance of the pyr locus to the centromere? Show your work.
In Figure 15-3a, what would the kernel phenotype be ifthe strain were homozygous for all dominant markers onchromosome 9?
. 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?
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)?
Trihybrid Cross: Several testcrosses have revealed the rate of recombination for the following genes which are KNOWN TO BE LINKED: k-m 0.30 k-l 0.76 l-m 0.50 What is the order of the three genes and why is the frequency of recombination between the closest pair of genes not equal to the recombination rate between the two genes farthest apart? (0.8 > 0.76)
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.
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.
Recombination frequencies between three loci in corn are shown in the following table: Loci Recombination frequency (%) R and W2 17 R and L2 35 W2 and L2 18 What is the order of the genes on the chromosome?
Figure 8.10 In pea plants, purple flowers (P) are dominant to white (p), and yellow peas (Y) are dominant to green (y). What are the possible genotypes and phenotypes for a cross between PpYY and ppYy pea plants? How many squares would you need to complete a Punnett square analysis of this cross?