120 Review Questions

5. Mendel performed hybridizations by transferring pollen from the _______ of the male plant to the female ova.

1. anther
2. pistil
3. stigma
4. seed

6. Which is one of the seven characteristics that Mendel observed in pea plants?

1. flower size
2. seed texture
3. leaf shape
4. stem color

7. Imagine you are performing a cross involving seed color in garden pea plants. What F1 offspring would you expect if you cross true-breeding parents with green seeds and yellow seeds? Yellow seed color is dominant over green.

1. 100 percent yellow-green seeds
2. 100 percent yellow seeds
3. 50 percent yellow seeds, 50 percent green seeds
4. 25 percent green seeds, 75 percent yellow seeds

8. Consider a cross to investigate the pea pod texture trait, involving constricted or inflated pods. Mendel found that the traits behave according to a dominant/recessive pattern in which inflated pods were dominant. If you performed this cross and obtained 650 inflated-pod plants in the F₂ generation, approximately how many constricted-pod plants would you expect to have?

1. 600
2. 165
3. 217
4. 468

9. A scientist pollinates a true-breeding pea plant with violet, terminal flowers with pollen from a true-breeding pea plant with white, axial flowers. Which of the following observations would most accurately describe the F₂ generation?

1. 75% violet flowers, 75% terminal flowers
2. 75% white flowers in a terminal position
3. 75% violet flowers, 75% axial flowers
4. 75% violet flowers in an axial position

10. The observable traits expressed by an organism are described as its ________.

1. phenotype
2. genotype
3. alleles
4. zygote

11. A recessive trait will be observed in individuals that are ________ for that trait.

1. heterozygous
2. homozygous or heterozygous
3. homozygous
4. diploid

12. If black and white true-breeding mice are mated and the result is all gray offspring, what inheritance pattern would this be indicative of?

1. dominance
2. codominance
3. multiple alleles
4. incomplete dominance

13. The ABO blood groups in humans are expressed as the I^A, I^B, and i alleles. The I^A allele encodes the A blood group antigen, IB encodes B, and i encodes O. Both A and B are dominant to O. If a heterozygous blood type A parent (I^Ai) and a heterozygous blood type B parent (I^Bi) mate, one quarter of their offspring will have AB blood type (I^AI^B) in which both antigens are expressed equally. Therefore, ABO blood groups are an example of:

1. multiple alleles and incomplete dominance
2. codominance and incomplete dominance
3. incomplete dominance only
4. multiple alleles and codominance

14. In a mating between two individuals that are heterozygous for a recessive lethal allele that is expressed in utero, what genotypic ratio (homozygous dominant:heterozygous:homozygous recessive) would you expect to observe in the offspring?

1. 1:2:1
2. 3:1:1
3. 1:2:0
4. 0:2:1

15. If the allele encoding polydactyly (six fingers) is dominant, why do most people have five fingers?

1. Genetic elements suppress the polydactyl gene.
2. Polydactyly is embryonic lethal.
3. The sixth finger is removed at birth.
4. The polydactyl allele is very rare in the human population.

16. A farmer raises black and white chickens. To his surprise, when the first generation of eggs hatch, all the chickens are black with white speckles throughout their feathers. What should the farmer expect when the eggs laid after interbreeding the speckled chickens hatch?

1. All the offspring will be speckled.
2. 75% of the offspring will be speckled, and 25% will be black.
3. 50% of the offspring will be speckled, 25% will be black, and 25% will be white.
4. 50% of the offspring will be black, and 50% of the offspring will be white.

17. Assuming no gene linkage, in a dihybrid cross of AABB x aabb with AaBb F₁ heterozygotes, what is the ratio of the F₁ gametes (AB, aB, Ab, ab) that will give rise to the F₂ offspring?

1. 1:1:1:1
2. 1:3:3:1
3. 1:2:2:1
4. 4:3:2:1

18. The forked line and probability methods make use of what probability rule?

1. test cross
2. product rule
3. monohybrid rule
4. sum rule

19. How many different offspring genotypes are expected in a trihybrid cross between parents heterozygous for all three traits when the traits behave in a dominant and recessive pattern? How many phenotypes?

1. 64 genotypes; 16 phenotypes
2. 16 genotypes; 64 phenotypes
3. 8 genotypes; 27 phenotypes
4. 27 genotypes; 8 phenotypes

20. Labrador retrievers’ fur color is controlled by two alleles, E and B. Any dog with the ee__ genotype develops into a yellow lab, while B_E_ dogs become black labs and bbE_ dogs become chocolate labs. This is an example of _____.

1. epistasis
2. codominance
3. incomplete dominance
4. linkage

21. Which of the following situations does not follow the Law of Independent Assortment?

1. A blond person and a brown-haired person produce three offspring over time, all of who have blond hair.
2. A white cow crossed with a brown bull produces roan cattle.
3. Mating a hog with a sow produces six female piglets.
4. Men are more likely to experience hemophilia than women.