Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

The heterozygote has a phenotype that is intermediate between the two homozygotes.

Question 2

A cat with genotype $$w^s w^s$$, $$CC is $$observed. What will its fur look like?

Accepted Answer

Pigmented (has color everywhere)

Question 3

In snapdragons, flower color is determined by the $$C^R$$ and $$C^I$$ alleles. $$C^R$$ produces red pigment, $$C^I$$ produces no pigment. What is the expected phenotype of a $$C^R C^I$$ plant?

Accepted Answer

Pink flowers

Question 4

Which of the following is an example of co-dominance?

Accepted Answer

A heterozygote expressing both alleles distinctly, such as AB blood type in humans

Question 5

A mutation in a gene results in a protein that is present but has only partial function compared to the wild type. What is the term for this type of mutation?

Accepted Answer

Hypomorphic mutation

Question 6

A patient has a dominant allele for polydactyly, but only 70% of individuals with this allele show the extra digit phenotype. What genetic concept does this illustrate?

Accepted Answer

Incomplete penetrance

Question 7

Which of the following best describes a dominant negative mutation?

Accepted Answer

A mutation that results in a protein that interferes with the function of the wild type protein

Question 8

A yeast strain with genotype $$nn is $$resistant to the drug canavanine. What is the most likely explanation for this resistance?

Accepted Answer

The $$n$$ allele encodes a non-functional transporter, so canavanine cannot enter the cell.

Question 9

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both fur color and hearing in cats

Question 10

A mutation in the lactase gene promoter causes lactase to be expressed into adulthood, resulting in lactose tolerance. What type of mutation is this?

Accepted Answer

Gain of function (hypermorphic)

Question 11

Which of the following statements about gain of function (GOF) mutations is correct?

Accepted Answer

GOF mutations often result in a protein with increased or new activity.

Question 12

A cat with genotype $$w^s w^s$$, $$cc is $$observed. What will its fur look like?

Accepted Answer

Completely white

Question 13

Which of the following best explains why most loss of function (LOF) mutations are recessive?

Accepted Answer

Because one functional copy of the gene is usually sufficient for normal function

Question 14

A heterozygote for a gene has only half the normal amount of functional protein, and this is not enough for a normal phenotype. What is this phenomenon called?

Accepted Answer

Haploinsufficiency

Question 15

Which of the following is a real-world example of a conditional loss of function mutation?

Accepted Answer

A temperature-sensitive tyrosinase allele in Siamese cats that only produces pigment in cooler body regions

Question 16

Which of the following best describes the molecular basis for dominance between two alleles?

Accepted Answer

The dominance is determined by the activity of the protein products of the alleles.

Question 17

A mutation causes a protein to be expressed in a tissue where it is not normally found, resulting in a new phenotype. What is this type of mutation called?

Accepted Answer

Neomorphic mutation

Question 18

Which of the following equations correctly represents the expected phenotypic ratio for a monohybrid cross with complete dominance?

Accepted Answer

$$3:1$$

Question 19

In a population, a gene has three alleles: $$A_1$$, $$A_2$$, and $$A_3. If$$ $$A_1 is $$dominant to both $$A_2$$ and $$A_3$$, and $$A_2 is $$dominant to $$A_3$$, what is the order of dominance?

Accepted Answer

$$A_1$$ \u003e $$A_2$$ \u003e $$A_3$$

Question 20

A protein is only functional when four subunits assemble together. A mutation in one allele produces a non-functional subunit that disrupts the function of the entire complex, even in the presence of wild type subunits. What is this an example of?

Accepted Answer

Dominant negative mutation

Genetic Interactions and Dominance Relationships in Genetics

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