Question 1

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

Accepted Answer

An allele that leads to enhanced protein function, such as higher expression or activity.

Question 2

A mutation causes the rhodopsin gene to be constantly active in rod cells, leading to overstimulation. What type of mutation is this?

Accepted Answer

Hypermorphic gain-of-function (GOF) mutation

Question 3

Which scenario best illustrates a neomorphic mutation?

Accepted Answer

A normal protein is produced in a tissue where it is not usually found.

Question 4

In humans, lactose tolerance is due to a GOF mutation that causes lactase to be produced beyond infancy. What is the molecular basis for this phenotype?

Accepted Answer

A mutation in the promoter region that keeps the gene ON after weaning.

Question 5

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, which are less likely than disruptions.

Question 6

A patient has a mutation that causes a normal protein to be produced at the wrong time, leading to disease. This is an example of:

Accepted Answer

Gain-of-function mutation affecting gene regulation

Question 7

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

Accepted Answer

The protein is completely absent.

Question 8

If an individual is heterozygous for two alleles of a gene, what can be determined about the relationship between those alleles?

Accepted Answer

The dominance relationship between the alleles.

Question 9

A mutation in the Antennapedia gene causes legs to develop where antennae should be in Drosophila. This is best described as:

Accepted Answer

A neomorphic gain-of-function mutation

Question 10

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

Accepted Answer

$$A_{mut} \u003e A_{WT}$$

Question 11

In a population where lactose intolerance is common, what is the most likely explanation for the distribution of the lactase gene mutation?

Accepted Answer

The mutation for lactase persistence did not arise or was not selected for in these populations.

Question 12

Which of the following best describes the effect of a neomorphic mutation?

Accepted Answer

The protein is made at the wrong time or place, or has a new activity.

Question 13

A gene promoter mutation causes continuous expression of a gene that is normally turned off after childhood. What is the most likely consequence?

Accepted Answer

The protein will be produced throughout life, possibly leading to a new phenotype.

Question 14

Which of the following is a real-world example of a gain-of-function mutation causing disease?

Accepted Answer

A mutation in a proto-oncogene leading to cancer.

Question 15

If a gene is expressed in a tissue where it is not normally found due to a mutation, what type of mutation is this?

Accepted Answer

Neomorphic gain-of-function mutation

Question 16

Which of the following statements about the heterozygous state is correct?

Accepted Answer

It allows determination of the dominance relationship between two alleles.

Question 17

A mutation causes a protein to gain a new enzymatic activity not present in the wild type. This is an example of:

Accepted Answer

Neomorphic gain-of-function mutation

Question 18

Which of the following best explains why the heterozygous state is informative in genetic analysis?

Accepted Answer

It reveals the interaction between two different alleles for a gene.

Question 19

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

Accepted Answer

Lack of selection for lactase persistence due to absence of dairy in the diet.

Question 20

Which of the following equations best represents the gene expression profile for a GOF mutation causing persistent lactase production?

Accepted Answer

$$E_{mut}(t) = E_{WT}(t)$$ for $$t  E_{WT}(t)$$ for $$t \geq 5$$

Gain-of-Function (GOF) Mutations: Mechanisms and Phenotypic Effects

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