Exam 14: Mendel and the Gene Idea

Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes eye problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F₂ generation. The results were as follows: 6,022 yellow and 2,001 green (8,023 total). Which of the following statements correctly describes the relationship of the allele for green seeds to the allele for yellow seeds?

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?

A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have the normal number of digits (five fingers on each hand and five toes on each foot.)Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third)child will have extra digits?

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?

Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F₁ generation and then reappeared in the F₂ generation?

One of two major forms of a human condition called neurofibromatosis (NF1)is inherited as a dominant gene, although it may range from mildly to very severely expressed. Which of the following is the best explanation for why a young, affected child is the first in her family to be diagnosed?

Why did all of the F₁ offspring of Mendel's classic pea cross always look like one of the two parental varieties?

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

Suppose two individuals with the genotype AaBbCc are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white. What is the most probable genotype of each parent?

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

In cattle, roan coat color (mixed red and white hairs)occurs in the heterozygous (CᴿCᵂ)offspring of red (CᴿCᴿ)and white (CᵂCᵂ)homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Use the figure and the following description to answer the question. In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1-4 correspond to plants that will be true-breeding?

Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of 13 years. Patients, who look very old even as children, do not live to reproduce. Which of the following statements represents the most likely assumption regarding this disorder?

Gene S controls the sharpness of spines in a type of cactus. Cacti with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cacti have dull spines. At the same time, a second gene, N, determines whether or not cacti have spines. Homozygous recessive nn cacti have no spines at all. If cacti heterozygous for both traits, SsNn, were allowed to self-pollinate, the offspring would segregate into which of the following phenotype ratios?

Skin color in a certain species of fish is inherited via a single gene with four different alleles. One fish of this type has alleles 1 and 3 (S₁S₃), and its mate has alleles 2 and 4 (S₂S₄). If each allele confers a unit of color darkness such that S₁ has one unit, S₂ has two units, and so on, then what proportion of their offspring would be expected to have five units of color?

Mendel continued some of his experiments into the F₂ or F₃ generation in order to ________.

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following correctly describes why this situation is possible?

Which of the following statements is a correct explanation for the observation that all offspring exhibit a phenotype for a particular trait that appears to be a blend of the two parental varieties?