4. Tightly curled hair is caused by a dominant autosomal gene in humans. This tr

Question

4. Tightly curled hair is caused by a dominant autosomal gene in humans. This trait is rare among northern Europeans. If a curly-haired northern European marries a person with straight hair, what phenotypes (and in what proportions) are expected in the offspring?
A. 1/2 curly (because the curly-haired individual is most likely heterozygous), 1/2 straight hair
B. 1/2 curly (because the curly-haired individual is most likely homozygous), 1/2 straight hair
C. all curly (because the curly-haired individual is most likely heterozygous)
D. 3/4 curly (because the curly-haired individual is most likely heterozygous), 1/4 straight hair
E. none of the above
A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino
was crossed with a second black animal, 6 blacks and 6 albinos were obtained. What is the best explanation for this genetic situation?
A. Albino is recessive; black is dominant.
B. Albino is dominant; black is incompletely dominant.
C. Albino and black are codominant.
D. Albino is recessive; black is recessive.
E. None of the above apply.
How many unique gametes could be produced through independent assortment by an individual with
the genotype AaBbCCDdEE?
A. 32
B. 4
C. 16
D. 8
E. 1/64
Assuming independent assortment for all gene pairs, what is the probability that the following parents,
AABbCc × AaBbCc, will produce an AaBbCc offspring?
A. 1/2
B. 1/16
C. 1/8
D. 3/4
E. 9/16

Explanation / Answer

A. It is true that the curly haired person is most likely to be heterozygous, and straight hair is obviously recessive, so the answer has to be A A.The Albino trait is definitively recessive as shown by the first test cross. And the second cross shows that the trait for albinism by the 50/50 split in progeny. Answer A D. The number of individual meiotic gametes is doubled with every trait that includes two alleles. the single allele traits are not to be included in the final calculation as they are considered constant. therefore 2x2x2=8 possible individual alleles... C. The probability of any particular genotype emerging from given alleles is the product of the probability of each individual cross with a heterozygous monohybrid cross. the probability of each of the monohybrid components in this trihybrid cross is each 1/2. Therefore: 1/2 x 1/2 x 1/2=1/8

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