Ch. 5 - Chromosome Mapping in Eukaryotes
Chapter 5, Problem 10
Colored aleurone in the kernels of corn is due to the dominant allele R. The recessive allele r, when homozygous, produces colorless aleurone. The plant color (not the kernel color) is controlled by another gene with two alleles, Y and y. The dominant Y allele results in green color, whereas the homozygous presence of the recessive y allele causes the plant to appear yellow. In a testcross between a plant of unknown genotype and phenotype and a plant that is homozygous recessive for both traits, the following progeny were obtained: colored, green 88 colored, yellow 12 colorless, green 8 colorless, yellow 92 Explain how these results were obtained by determining the exact genotype and phenotype of the unknown plant, including the precise arrangement of the alleles on the homologs.
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Textbook Question
What is the proposed basis for positive interference?
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Textbook Question
What two essential criteria must be met in order to execute a successful mapping cross?
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Textbook Question
The genes dumpy (dp), clot (cl), and apterous (ap) are linked on chromosome II of Drosophila. In a series of two-point mapping crosses, the following genetic distances were determined. What is the sequence of the three genes?
dp–ap 42
dp–cl 3
ap–cl 39
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Textbook Question
In the cross shown here, involving two linked genes, ebony (e) and claret (ca), in Drosophila, where crossing over does not occur in males, offspring were produced in a 2 + : 1 ca : 1 e phenotypic ratio:
These genes are 30 units apart on chromosome III. What did crossing over in the female contribute to these phenotypes?
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Textbook Question
In a series of two-point mapping crosses involving five genes located on chromosome II in Drosophila, the following recombinant (single-crossover) frequencies were observed:
pr–adp 29%
pr–vg 13
pr–c 21
pr–b 6
adp–b 35
adp–c 8
adp–vg. 16
vg–b. 19
vg–c 8
c–b. 27
Given that the adp gene is near the end of chromosome II (locus 83), construct a map of these genes.
794
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Textbook Question
In a series of two-point mapping crosses involving five genes located on chromosome II in Drosophila, the following recombinant (single-crossover) frequencies were observed:
pr–adp 29%
pr–vg 13
pr–c 21
pr–b 6
adp–b 35
adp–c 8
adp–vg. 16
vg–b. 19
vg–c 8
c–b. 27
In another set of experiments, a sixth gene, d, was tested against b and pr:
d–b 17%
d–pr 23%
Predict the results of two-point mapping between d and c, d and vg, and d and adp.
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