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27 Cards in this Set
- Front
- Back
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What do we mean when we use the terms monohybrid cross and dihybrid cross?
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A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.
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Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?
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One phenotype was completely dominant over another.
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What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
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Traits are inherited in discrete units, and are not the results of "blending."
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How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
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8
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Why did Mendel continue some of his experiments to the F2 or F3 generation?
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to observe whether or not a recessive trait would reappear
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Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?
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that the parents were both heterozygous for a single trait
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A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
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HT
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When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
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50%
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Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that
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traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
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The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
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All of the genes controlling the traits behaved as if they were on different chromosomes.
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Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?
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anaphase I of meiosis
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Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?
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alignment of tetrads at the equator
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Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?
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1/2
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In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
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0
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In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
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1/64
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Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent
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3/4
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Which of the following calculations require that you utilize the addition rule?
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Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.
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In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red : 2 roan :1 white?
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roan × roan
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Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
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pleiotropy
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Which of the following is an example of polygenic inheritance?
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skin pigmentation in humans
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Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following
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environmental factors such as soil pH
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Which of the following provides an example of epistasis?
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In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.
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A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?
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Design a test for identifying heterozygous carriers of the allele.
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An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?
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blood transfusion
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The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?
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Darwin's explanation of natural selection
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One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?
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One of the parents has very mild expression of the gene.
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Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?
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TtRr—tall and pink
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