Question 1

In a dihybrid cross involving recessive epistasis (e.g., coat color in mice), what is the expected phenotypic ratio among the offspring if both parents are heterozygous for both genes (AaBb x AaBb)?

Accepted Answer

$$9:3:4$$

Question 2

A plant with genotype AaBb is crossed with another plant of the same genotype. If the two genes interact via dominant epistasis (e.g., squash color), what proportion of the offspring will display the white phenotype?

Accepted Answer

$$12/16$$

Question 3

Which of the following best describes the genetic interaction known as complementation?

Accepted Answer

Both genes must have at least one dominant allele for the wildtype phenotype to be expressed.

Question 4

In a redundancy gene interaction (e.g., seed capsule shape), what is the expected phenotypic ratio in the F2 generation from a cross of two double heterozygotes (AaBb x AaBb)?

Accepted Answer

$$15:1$$

Question 5

A fruit fly with genotype AaBb (where A = brown pigment, B = red pigment) is crossed with another of the same genotype. If both genes contribute independently to eye color and together produce a novel phenotype, what is the expected ratio of wildtype (brick red), brown, scarlet, and white eyes in the offspring?

Accepted Answer

$$9:3:3:1$$

Question 6

In an additive gene interaction affecting squash shape, what phenotype would you expect from a plant with genotype Aabb?

Accepted Answer

Sphere

Question 7

Suppose in a suppression interaction (Rec/Rec) in fruit fly eye color, gene A (A = wildtype, a = vermillion) and gene B (B = no suppression, b = suppression), what is the expected phenotypic ratio in the F2 generation from AaBb x AaBb?

Accepted Answer

$$13:3$$

Question 8

A researcher observes a 9:7 phenotypic ratio in the F2 generation of a dihybrid cross. Which gene interaction is most likely responsible for this ratio?

Accepted Answer

Complementation

Question 9

In a dominant epistasis interaction, which genotype combination will result in the green phenotype in squash?

Accepted Answer

aabb

Question 10

If a plant with genotype aaBb (where A and B both shorten seed capsule shape additively) is self-crossed, what is the expected proportion of offspring with the 'long' phenotype?

Accepted Answer

$$1/16$$

Question 11

Which of the following best explains the difference between additive and novel gene interactions?

Accepted Answer

Additive interactions combine effects to intensify a shared trait, while novel interactions produce a new phenotype not seen in either single mutant.

Question 12

A geneticist crosses two plants, both with genotype AaBb, where both genes are required for purple pigment production (complementation). What fraction of the offspring will be albino?

Accepted Answer

$$7/16$$

Question 13

In a suppression interaction (Dom/Dom), which genotype will result in the vermillion phenotype in fruit fly eye color?

Accepted Answer

A_bb

Question 14

A cross between two AaBb plants (where A = black, a = agouti, B = expression allowed, b = expression not allowed) produces which phenotypic ratio in the offspring?

Accepted Answer

$$9$$ black : $$3$$ agouti : $$4$$ white

Question 15

In a redundancy interaction, which genotype will result in the ovoid phenotype for seed capsule shape?

Accepted Answer

aabb

Question 16

A fruit fly with genotype aaBb (A = brown pigment, B = red pigment) will have which eye color phenotype in a novel gene interaction?

Accepted Answer

Scarlet eyes

Question 17

In a suppression interaction (Rec/Dom), what is the expected phenotypic ratio in the F2 generation from a cross of two double heterozygotes?

Accepted Answer

$$9:7$$

Question 18

Which of the following scenarios best illustrates dominant epistasis?

Accepted Answer

A dominant allele at one locus masks the expression of alleles at a second locus, resulting in a 12:3:1 ratio.

Question 19

If a plant with genotype Aabb (where A and B both shorten seed capsule shape additively) is crossed with itself, what is the expected proportion of offspring with the 'disc' phenotype?

Accepted Answer

$$9/16$$

Question 20

A geneticist observes a 9:3:3:1 phenotypic ratio in the F2 generation of a dihybrid cross. Which type of gene interaction is most likely responsible?

Accepted Answer

Novel gene interaction

Gene Interactions and Modified Mendelian Ratios

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