Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

Heterozygotes display a phenotype that is intermediate between the two homozygotes.

Question 2

In the ABO blood group system, which genotype(s) result in type AB blood?

Accepted Answer

$$I^A I^B$$

Question 3

A mutation that results in a gene product with increased activity compared to the wild type is called:

Accepted Answer

Hypermorphic mutation

Question 4

Which of the following is an example of codominance?

Accepted Answer

A flower with both red and white patches on its petals

Question 5

In the C-gene allelic series for mammalian coat color, which genotype results in a Himalayan phenotype?

Accepted Answer

$$c^h c^h$$

Question 6

A cross between two true-breeding yellow mice produces offspring in a 2:1 ratio of yellow to agouti. Which genetic phenomenon explains this result?

Accepted Answer

A dominant lethal allele

Question 7

Which of the following best describes epistasis?

Accepted Answer

The alleles of one gene mask or modify the expression of alleles of another gene

Question 8

In Labrador retrievers, the coat color is determined by two genes. If a dog has the genotype $$bbEE$$, what will be its coat color?

Accepted Answer

Chocolate

Question 9

A cross between two plants produces F2 offspring in a 9:7 ratio of purple to white flowers. Which type of gene interaction is most likely responsible?

Accepted Answer

Complementary gene interaction

Question 10

Which of the following genotypes would result in an albino rabbit in the C-gene allelic series?

Accepted Answer

$$cc$$

Question 11

If a gene mutation results in a complete loss of function, what is this mutation called?

Accepted Answer

Null (amorphic) mutation

Question 12

In a dihybrid cross with no gene interaction, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 13

Which of the following is true about haplosufficient alleles?

Accepted Answer

One copy of the allele is sufficient to produce the wild-type phenotype

Question 14

A plant with genotype $$AAbb is $$crossed with a plant with genotype $$aaBB. If $$the two genes show duplicate gene interaction, what phenotype will the F1 generation display?

Accepted Answer

Wild-type phenotype

Question 15

Which of the following best describes a neomorphic mutation?

Accepted Answer

A mutation that results in a novel gene activity not found in the wild type

Question 16

In a population, a gene has four alleles with the following dominance hierarchy: $$A \u003e B \u003e C \u003e D. $$Which genotype will express the phenotype associated with allele B?

Accepted Answer

$$BB$$

Question 17

A cross between two true-breeding squash plants, one with disk-shaped fruit ($$AABB) $$and one with long fruit ($$aabb$$), produces F2 offspring in a 9:6:1 ratio of disk: sphere: long. What type of gene interaction is this?

Accepted Answer

Dominant gene interaction

Question 18

Which of the following is an example of a leaky (hypomorphic) mutation?

Accepted Answer

A mutation that reduces but does not eliminate enzyme activity

Question 19

In a cross involving dominant epistasis, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$12:3:1$$

Question 20

Which of the following best explains why the $$I^A$$ and $$I^B$$ alleles in the ABO blood group system are considered codominant?

Accepted Answer

Both alleles are expressed and produce distinct antigens on the surface of red blood cells

Gene Interactions and Their Effects on Phenotype

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