Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 21, Problem 26P
You have identified an autosomal gene that contributes to tail size in male guppies, with a dominant allele B for large tails and a recessive allele b for small tails. Female guppies of all genotypes have similar tail sizes. You know that female guppies usually mate with males with the largest tails, but the effects of population density and the ratio of the sexes on this preference have not been studied. You therefore place an equal number of males in three tanks. In tank 1, the number of females is twice the number of males. In tank 2, the numbers of males and females are equal. In tank 3, half as many females as males are present. After mating, you find the following proportions of small-tailed males among the progeny: tank 1, 16%; tank 2, 25%; tank 3, 30%.
| a. | In your original population (before the animals were placed in the three tanks), 25% of the males have small tails. Assuming that the allele frequencies in males and females are the same, calculate the frequencies of B and b in your original population. |
| b. | Calculate Δq for each tank. |
| c. | If WBB = 1.0, what is WBb for each tank? |
| d. | If WBB = 1.0, is Wbb less than, equal to, or greater than 1.0 for each tank? |
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Calculate the observed allele frequencies, using p for the frequency of allele G, and the expected number of giraffes of each phenotype assuming Hardy-Weinberg Equilibrium (do not do the entire chi-square calculation!). For frequencies, report four positions after the decimal. For expected numbers, report two positions after the decimal.
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You are studying a population of giraffes. In this population, one gene (G) controls spot color in
giraffes, which shows incomplete dominance. Individuals with white spots are homozygous gg,
individuals with brown spots are homozygous GG, and heterozygotes have orange spots (Gg). You
observe 25 white-spotted giraffes, 15 orange-spotted giraffes, and 22 brown-spotted giraffes.
Calculate the observed allele frequencies, using p for the frequency of allele G, and the expected
number of giraffes of each phenotype assuming Hardy-Weinberg Equilibrium (do not do the entire
chi-square calculation!). For frequencies, report four positions after the decimal. For expected
numbers, report two positions after the decimal.
• p=
• q =
• Expected number of orange-spotted =
• Expected number of brown-spotted =
Expected number of white-spotted
=
Imagine you are studying a population of finches on one of the Galápagos Islands. You have been recording many of the birds’ physical traits, including the length of both wings. You observe that for 80% of individuals measured, the length of the left wing is not significantly different from the length of the right wing (in other words, they are symmetrical). But for about 20% of birds measured, the wing lengths are asymmetrical. This distribution is true from generation to generation. Suddenly, a rare 5-day windstorm takes over the island. After the storm, you spend the next several days netting each bird on the island that survived the storm. You discover that 85% of the birds with symmetrical wings survived the storm, whereas only 5% of the birds with asymmetrical wings did.
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Chapter 21 Solutions
Genetics: From Genes to Genomes
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