Lesson Worksheet: Complementary Genes Biology

In this worksheet, we will practice describing the effect of complementary genes on gene expression, and applying this to given examples.

Q1:

Assume fur color in mice is an example of a characteristic affected by complementary gene action. The fur can be white or black; in this scenario, there must be a dominant allele present for both genes for the black color to be shown.

Which of the following genotypes would give a mouse with white fur?

  • AAaBb
  • BaaBB
  • CAABB
  • DAABb
  • EAaBB

Q2:

Assume fur color in mice is an example of a characteristic affected by complementary gene action. The fur can be white or black; in this scenario, there must be a dominant allele present for both genes for the black color to be shown.

Which of the following genotypes would give a mouse black fur?

  • AaaBB
  • BAAbb
  • CAabb
  • DAaBb
  • EAll of the above

Q3:

The color of sweet pea flowers is determined by two genes and their complementary action. The table provided shows the genotypes of different sweet pea plants.

GenotypePhenotypeEnzyme AEnzyme B
AABBPurpleFunctionalFunctional
AabbWhiteYNonfunctional
aabbXNonfunctionalZ

What should replace X?

  • APurple
  • BWhite

What should replace Y?

  • ANonfunctional
  • BFunctional

What should replace Z?

  • AFunctional
  • BNonfunctional

Q4:

The Punnett square shows the phenotypes resulting from a cross between mice that are heterozygous for fur color. What are the missing alleles?

  • AaB
  • Bab
  • CAb
  • DAB

Q5:

Which of the following best defines the term complementary genes?

  • AComplementary genes are genes that inhibit the production of complement proteins.
  • BComplementary genes are two genes that are simultaneously expressed in the phenotype.
  • CComplementary genes are two or more different genes that work together to contribute to a particular trait.
  • DComplementary genes are genes that “mix” together to produce a new, distinct phenotype.

Q6:

Complete the following statements about alleles.

An allele that is always expressed in the phenotype when present is known as .

  • Amutated
  • Bprominent
  • Cdiploid
  • Drecessive
  • Edominant

An allele that is only expressed in the phenotype when two copies are present is known as .

  • Arecessive
  • Bsubmissive
  • Chaploid
  • Dmutated
  • Edominant

Q7:

Flower color in sweet pea plants is an example of a characteristic affected by complementary gene action. The flowers can be white or purple; in this scenario, there must be a dominant allele present for both genes for the purple flower color to be shown.

Which of the following genotypes would give a plant with white flowers?

  • AAaBB
  • BAABb
  • CAaBb
  • DaaBB
  • EAABB

Q8:

Assume that fur color in mice is controlled by complementary genes. The diagram provided shows the biochemical pathway that results in a mouse having black fur. What will happen if enzyme B is no longer functional?

  • AThe mouse will have no fur.
  • BThe mouse will die.
  • CThe fur will be white/colorless.
  • DThe fur will be black.

Q9:

Assume that the color of fur in mice is determined by two genes and their complementary action. The table provided shows the genotypes of different mice.

GenotypePhenotypeEnzyme AEnzyme B
AABBBlackFunctionalZ
aabbWhiteYNonfunctional
AaBbXFunctionalFunctional

What should replace X?

  • ABlack
  • BWhite

What should replace Y?

  • ANonfunctional
  • BFunctional

What should replace Z?

  • AFunctional
  • BNonfunctional

Q10:

Flower color in sweet pea plants is an example of a characteristic affected by complementary gene action. The flowers can be white or purple; in this scenario, there must be a dominant allele present for both genes for the purple flower color to be shown.

Which of the following genotypes would give a plant with purple flowers?

  • AAabb
  • BaaBB
  • Caabb
  • DAaBb
  • EAAbb

This lesson includes 19 additional questions for subscribers.

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