BIOLOGY 100 - Human Biology
GENETICS PRACTICE PROBLEMS
Part 2
Question 1
Use the Punnett square to determine all of the offspring genotypes (and their relative frequencies) from the following crosses (assume independent assortment):
a. RrYy x RrYy
b. RrYy x rryy
c. RrYy x Rryy
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Question 2
In the problem above, the "R" allele is a dominant allele specifying for round seeds (in peas), while the "r" allele is the recessive allele specifying for wrinkled seeds; in addition, the "Y" allele specifies for the dominant yellow seed color trait, while "y" specifies for green seeds (recessive). Give the expected frequencies (as percentages or ratios) for the phenotypes of the offspring resulting from each of the crosses above.
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Question 3
In turkeys a dominant gene R produces the familiar bronze color; its recessive allele r results in red. Another dominant gene H results in normal feathers; its recessive allele h produces feathers without webbing, so that they resemble tufts of hair. Two bronze turkeys with normal feathers were mated, and their offspring consisted of 8 bronze with normal feathers, three bronze with hairy feathers, two red with normal feathers, and one red with hairy feathers. What were the genotypes of the parents?
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Question 4
In horses black is dependent upon a dominant gene, B, and chestnut upon its recessive allele, b. The trotting gait is due to a dominant allele T, and the pacing gait to its recessive allele, t. If a homozygous black pacer is mated to a homozygous chestnut trotter, what will be the appearance of the F1 generation?
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Question 5
Referring to the previous question (Question 4), what would be the genotypes and phenotypes (and their expected ratios or percentages) of the offspring produced by a mating between an F1 generation individual and a chestnut pacer?
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Question 6
Assume right-handedness (R) dominates over left-handedness (r) in humans, and that brown eyes (B) are dominant over blue (b). A right-handed, blue-eyed man marries a right-handed, brown-eyed woman. One of their two children is right-handed/blue-eyed, while the other is left-handed/brown-eyed. The man marries again, and this time the woman is right-handed and brown-eyed. They have 10 children, all right-handed and brown-eyed. What are the genotypes of the husband and two wives?
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revised 21 August 2001