Question 1

Which of the following best describes a hypermorphic allele resulting from a gain-of-function (GOF) mutation?

Accepted Answer

It leads to increased expression or activity of the gene product compared to wild type.

Question 2

A mutation in the rhodopsin gene causes constant stimulation of rod cells in the retina. This is an example of which type of mutation?

Accepted Answer

Hypermorphic gain-of-function (GOF) mutation

Question 3

In the context of lactose tolerance in humans, a GOF mutation in the gene promoter leads to which of the following outcomes?

Accepted Answer

Lactase is produced throughout adulthood, allowing digestion of lactose.

Question 4

Which scenario best illustrates a neomorphic mutation?

Accepted Answer

A gene product acquires a new function not present in the wild type.

Question 5

In Drosophila, a mutation causes the Antennapedia gene to be expressed in the head, resulting in legs instead of antennae. What type of mutation is this?

Accepted Answer

Neomorphic gain-of-function mutation

Question 6

Why are gain-of-function (GOF) mutations generally rarer than loss-of-function (LOF) mutations?

Accepted Answer

GOF mutations require specific changes that enhance or alter protein function, while LOF mutations can result from many types of disruptions.

Question 7

A person is heterozygous for the lactase gene promoter: one wild-type allele and one mutant allele that keeps the gene ON in adulthood. What is the expected phenotype?

Accepted Answer

Lactose tolerance, because the mutant allele is dominant.

Question 8

Which equation best represents the relationship between gene expression and protein activity in a hypermorphic allele?

Accepted Answer

$$A_{mutant} \u003e A_{WT}$$

Question 9

A population has a high frequency of lactose intolerance. Which historical factor most likely contributed to this distribution?

Accepted Answer

Mutations allowing lactase persistence did not occur or were not selected for.

Question 10

Which of the following is NOT a possible outcome of a gain-of-function mutation?

Accepted Answer

The gene product is completely absent.

Question 11

In a genetic cross, the heterozygous state is informative because:

Accepted Answer

It allows determination of dominance relationships between alleles.

Question 12

Which of the following best explains why a GOF mutation in a proto-oncogene can lead to cancer?

Accepted Answer

It results in increased or uncontrolled activity, promoting cell proliferation.

Question 13

A mutation causes a normal protein to be produced in a tissue where it is not usually found. This is an example of:

Accepted Answer

Neomorphic mutation

Question 14

If a gene promoter mutation keeps the gene ON after age 15, as shown in the lactase activity graph, what is the effect on lactase activity?

Accepted Answer

Lactase activity remains high after age 15.

Question 15

Which of the following is a real-world example of a gain-of-function mutation causing a normal protein to be produced at the wrong time?

Accepted Answer

Lactase persistence in adults due to a promoter mutation

Question 16

Which statement about the dominance of alleles in the context of lactase persistence is correct?

Accepted Answer

The mutant allele conferring lactase persistence is dominant over the wild-type allele.

Question 17

Which of the following best describes the effect of a GOF mutation in the Antennapedia gene in Drosophila?

Accepted Answer

Legs are formed in the head due to ectopic expression.

Question 18

Which of the following equations represents the dominance of the mutant allele for lactase persistence?

Accepted Answer

$$L_{WT/mutant} = L_{mutant/mutant}$$

Question 19

Which of the following is NOT a feature of a gain-of-function mutation?

Accepted Answer

It always results in a loss of protein function.

Gain-of-Function (GOF) Mutations: Mechanisms, Examples, and Genetic Dominance

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