Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

The phenotype of the heterozygote is intermediate between the two homozygotes.

Question 2

A cross between two heterozygous snapdragon plants (Rr) results in red, pink, and white flowers in a 1:2:1 ratio. What type of inheritance is this an example of?

Accepted Answer

Incomplete dominance

Question 3

Which of the following best explains why the ABO blood group system in humans is an example of codominance?

Accepted Answer

The IA and IB alleles are both expressed in the phenotype of individuals with genotype IAIB.

Question 4

A recessive lethal allele is present in a population. If two heterozygotes are crossed, what is the expected phenotypic ratio among the surviving offspring?

Accepted Answer

$$2:1$$

Question 5

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects multiple traits, such as Marfan syndrome affecting connective tissue, heart, and vision.

Question 6

In a biochemical pathway, if a mutation in gene A prevents the production of enzyme 1, which is required for the first step, what will be the result?

Accepted Answer

The precursor molecule will accumulate and the final product will not be made.

Question 7

Which genetic test is used to determine whether two mutations that result in the same phenotype are in the same gene or in different genes?

Accepted Answer

Complementation test

Question 8

In a dihybrid cross involving two genes that show recessive epistasis, what phenotypic ratio is expected in the F2 generation?

Accepted Answer

$$9:3:4$$

Question 9

Which of the following best describes dominant epistasis?

Accepted Answer

A dominant allele at one gene masks the expression of alleles at a second gene.

Question 10

A cross between two plants results in a 9:7 phenotypic ratio in the F2 generation. What is the most likely explanation?

Accepted Answer

Complementary gene action (duplicate recessive epistasis)

Question 11

Which of the following statements about complementation is correct?

Accepted Answer

If two mutations fail to complement, they are likely in the same gene.

Question 12

In a biochemical pathway, gene A acts before gene B. If gene A is mutated and nonfunctional, what is the effect on the pathway?

Accepted Answer

The pathway will be blocked at the step catalyzed by gene A, regardless of gene B's status.

Question 13

Which of the following is an example of a real-world application of gene interaction in medicine?

Accepted Answer

Understanding how mutations in different genes can cause similar symptoms in genetic diseases, such as cystic fibrosis.

Question 14

If a cross between two mutant strains results in wild-type offspring, what does this indicate about the mutations?

Accepted Answer

They are likely in different genes.

Question 15

Which of the following best describes the concept of epistasis?

Accepted Answer

The interaction between alleles of different genes, where one gene masks the effect of another.

Question 16

A geneticist observes a 12:3:1 phenotypic ratio in the F2 generation of a dihybrid cross. Which type of gene interaction is most likely responsible?

Accepted Answer

Dominant epistasis

Question 17

Which of the following is true regarding the complementation test?

Accepted Answer

It determines whether two mutations are in the same or different genes.

Question 18

In a pathway where gene A acts before gene B, and both are required for pigment production, what phenotype would you expect from an organism homozygous for a loss-of-function mutation in gene A but wild-type for gene B?

Accepted Answer

No pigment produced

Question 19

Which of the following ratios is characteristic of duplicate dominant epistasis?

Accepted Answer

$$15:1$$

Question 20

A researcher performs a complementation test with four mutant haploid yeast strains and observes two complementation groups. What does this indicate?

Accepted Answer

There are two genes involved in the pathway.

Gene Interaction: Extensions of Mendelian Inheritance and Genetic Pathways

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