Characteristics and Traits

Review Questions

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

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

Hint:

A

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

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

Hint:

C

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

Hint:

D

The ABO blood groups in humans are expressed as the IA, IB, and i alleles. The IA 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 (IAi) and a heterozygous blood type B parent (IBi) mate, one quarter of their offspring will have AB blood type (IAIB) 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

Hint:

D

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

Hint:

C

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.

Hint:

D

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.

Hint:

C