Question 1

Which of the following best describes a transition mutation?

Accepted Answer

A substitution of a purine for a purine or a pyrimidine for a pyrimidine

Question 2

A patient is diagnosed with Huntington disease, which is caused by expanding nucleotide repeats. What is the molecular basis of this mutation?

Accepted Answer

An increase in the number of CAG repeats in the gene

Question 3

Which of the following mutations is most likely to result in a frameshift?

Accepted Answer

Deletion of one nucleotide

Question 4

A missense mutation is defined as:

Accepted Answer

A mutation that changes an amino acid to a different amino acid

Question 5

Which of the following is a characteristic of a somatic mutation?

Accepted Answer

It occurs in non-reproductive cells and is passed to daughter cells by mitosis

Question 6

Which repair mechanism is responsible for correcting mismatched bases that escape proofreading during DNA replication?

Accepted Answer

Mismatch repair

Question 7

Exposure to ultraviolet light can result in which type of DNA damage?

Accepted Answer

Formation of pyrimidine dimers

Question 8

Which of the following best explains the mutagenic effect of intercalating agents such as proflavin?

Accepted Answer

They insert themselves between adjacent bases, distorting the DNA helix and causing insertions or deletions

Question 9

A mutation that restores the wild-type phenotype in an organism that already has a mutant genotype is called:

Accepted Answer

Reverse mutation

Question 10

Which of the following is true about intragenic suppressor mutations?

Accepted Answer

They restore the original amino acid sequence by a second mutation within the same gene

Question 11

Which chemical agent is a base analog that can be incorporated into DNA and cause transition mutations?

Accepted Answer

5-Bromouracil

Question 12

What is the primary effect of depurination on DNA?

Accepted Answer

Loss of a purine base, potentially leading to base substitution

Question 13

Which DNA repair pathway removes and replaces bulky DNA lesions that distort the double helix?

Accepted Answer

Nucleotide-excision repair

Question 14

A mutation that results in the appearance of a trait in an inappropriate tissue or at an inappropriate time is best described as:

Accepted Answer

Gain-of-function mutation

Question 15

Which of the following factors does NOT directly affect the mutation rate in a population?

Accepted Answer

Number of chromosomes in the cell

Question 16

Transposable elements can cause mutations by:

Accepted Answer

Inserting into another gene and promoting DNA rearrangements

Question 17

Which of the following is a real-world example of a disease caused by defects in DNA repair systems?

Accepted Answer

Xeroderma pigmentosum

Question 18

A researcher exposes bacteria to stressful conditions and observes an increased mutation rate. This phenomenon is best described as:

Accepted Answer

Adaptive mutation

Question 19

Which of the following best describes the process of replicative transposition?

Accepted Answer

A new copy of the transposable element inserts in a new location, while the old copy stays behind

Question 20

Which DNA repair mechanism involves glycosylase enzymes recognizing and removing specific types of modified bases?

Accepted Answer

Base-excision repair

Gene Mutations and DNA Repair: Mechanisms, Types, and Effects

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