Genetic Analysis: An Integrated Approach (2nd Edition)
2nd Edition
ISBN: 9780321948908
Author: Mark F. Sanders, John L. Bowman
Publisher: PEARSON
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Chapter 21, Problem 20P
Suppose a polygenic system for producing color in ker-nels of a grain is controlled by three additive genes, G, M, and T. There are two alleles of each gene, GI and 02, MI and M2, and T1 and 72. The phenotypic effects of the three genotypes of the G gene are GIG, = 6 units of color, G1G2 = 3 units of color, and G2G2 = 1 unit of color. The phenotypic effects for genes M and T are similar, giving the phenotype of a plant with the genotype GIGIMIMITITI a total of 18 units of color and a plant with the genotype G2G2M2M2T2T2 a total of 3 units of color.
a) How many units of color are found in trihybrid plants?
b) Two trihybrid plants are mated. What is the expected proportion of progeny plants displaying 9 units of color? Explain your answer.
c) Suppose that instead of an additive genetic system, kernel-color determination in this organism is a thresh-old system. The appearance of color in kernels requires nine or more units of color; otherwise, kernels have no color and appear white. In other words, plants whose
d) Assuming the threshold model applies to this kernel-color system, what proportion of the progeny of the cross GIG2M1M2T2T2 x G 1 G2A/1/1/2Ti T2 do you expect to display colored kernels?
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In corn plants, a dominant allele (1) inhibits the expression of kernel color, while the recessive
allele (1) promotes the expression of kernel color when homozygous. Another dominant allele, (P),
causes purple kernel color, while the homozygous recessive genotype (pp) causes red kernels.
Assuming that these alleles assort independently, predict the phenotypic ratio of the offspring if
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Suppose a geneticist is using a three-point test cross to map three linked rabbit morphology and behavioral mutations called si,
It, and Le. The gene si is associated with the silky fur phenotype, and It is associated with the long-tailed phenotype. Both si and
It are recessive mutations with respect to wild type. Le is a dominant mutation that confers the lethargic phenotype.
The geneticist first crosses true-breeding lethargic rabbits to true-breeding silky fur, long-tailed rabbits. Next, the geneticist
backcrosses the Fj progeny to the silky fur, long-tailed parents, and obtains the results reported in the table.
Phenotype
Number
lethargic
815
silky fur, long-tailed
807
long-tailed
177
silky fur, lethargic
179
silky fur
7
long-tailed, lethargic
5
silky fur, long-tailed, lethargic
29
wild type
29
Place the genes in the correct order in the chromosome.
Answer Bank
si
It
Le
The shape of a pumpkin is determined by the action of two genes A and B. The recessive forms of these two alleles produces a flattened-shaped fruit, whereas the dominant forms of these two alleles produce the typical pumpkin with ridges. When both alleles are heterozygous a disc-shaped pumpkin is produced. If the genotype of the pumpkin plant is homozygous dominant at one allele and heterozygous at the other, the pumpkin will be ball-shaped. If the pumpkin plant is homozygous recessive at one allele and heterozygous at the other allele it produces an oblong-shaped fruit. Plants with genotypes other than the ones listed in this question do not produce pumpkins. Do the following cross: two pumpkin plants capable of making disc-shaped pumpkins are crossed with each other. Based on this cross, answer the following: (Show your work below.)
How many of the progeny will make ball-shaped pumpkins?__________________________________________
How many of the progeny will make disc-shaped…
Chapter 21 Solutions
Genetic Analysis: An Integrated Approach (2nd Edition)
Ch. 21 - Which of the following traits would you expect to...Ch. 21 - 19.2 For the traits listed in the previous...Ch. 21 - Compare and contrast broad sense heritability and...Ch. 21 - 19.4 In a cross of two pure-breeding lines of...Ch. 21 - 19.5 Describe the difference between continuous...Ch. 21 - Prob. 6PCh. 21 - 19.7 Provide a definition and an example for each...Ch. 21 - 19.10 Three pairs of genes with two alleles each (...Ch. 21 - Prob. 9PCh. 21 - 19.12 Two inbred lines of sunflowers produce...
Ch. 21 - Prob. 11PCh. 21 - 19.14 In Nicotiana, two inbred strains produce...Ch. 21 - 19.15 Suppose the length of maize ears has narrow...Ch. 21 - In a line of cherry tomatoes, the average fruit...Ch. 21 - 19.17 Two purebreeding wheat strains, one...Ch. 21 - Prob. 16PCh. 21 - During a visit with your grandparents, they...Ch. 21 - 19.20 An association of racehorse owners is...Ch. 21 - Prob. 19PCh. 21 - Suppose a polygenic system for producing color in...Ch. 21 - New Zealand lamb breeders measure the following...Ch. 21 - Cattle breeders would like to improve the protein...Ch. 21 - In human gestational development, abnormalities of...Ch. 21 - The children of couples in which one partner has...Ch. 21 - Answer the following in regard to multifactorial...
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