Question 1

Which of the following best describes a frameshift mutation, and what is its likely effect on the resulting protein?

Accepted Answer

An insertion or deletion of one or more nucleotides that shifts the reading frame, often resulting in a completely altered and nonfunctional protein.

Question 2

A patient is diagnosed with Marfan syndrome, which is caused by a loss-of-function mutation in the FBN1 gene. Which genetic concept does this illustrate?

Accepted Answer

Haploinsufficiency, where one functional copy of a gene is not sufficient to produce a normal phenotype.

Question 3

Which of the following is a correct example of a transition mutation?

Accepted Answer

A guanine (G) is replaced by an adenine (A).

Question 4

The Luria–Delbrück fluctuation test demonstrated that mutations in bacteria:

Accepted Answer

Occur spontaneously and randomly, not as a response to selective pressure.

Question 5

Which of the following DNA repair mechanisms specifically recognizes and repairs thymine dimers caused by UV light in bacteria, but is absent in humans?

Accepted Answer

Photoreactivation repair (PRE)

Question 6

A chemical mutagen that mimics the structure of a normal DNA base and increases the frequency of tautomeric shifts is called:

Accepted Answer

A base analog

Question 7

Which of the following best explains why individuals with xeroderma pigmentosum (XP) have a dramatically increased risk of skin cancer?

Accepted Answer

They have a defect in the nucleotide excision repair (NER) pathway, preventing the removal of UV-induced DNA lesions.

Question 8

A mutation in the HBB gene causes beta thalassemia, a blood disorder. Most of these mutations are:

Accepted Answer

Single nucleotide changes or small insertions/deletions.

Question 9

Which of the following is a real-world example of a disease caused by trinucleotide repeat expansion?

Accepted Answer

Huntington disease

Question 10

Which DNA repair mechanism uses a sister chromatid as a template to accurately repair double-strand breaks, and during which cell cycle phase is it most active?

Accepted Answer

Homologous recombination repair; late S or early G2 phase

Question 11

Which of the following statements about the Ames test is correct?

Accepted Answer

It measures the frequency of reverse mutations in Salmonella typhimurium to assess the mutagenicity of compounds.

Question 12

Which of the following is a likely consequence of an intercalating agent, such as ethidium bromide, interacting with DNA?

Accepted Answer

It causes base-pair distortions and DNA unwinding, leading to insertions or deletions during replication.

Question 13

A dominant negative mutation is best described as:

Accepted Answer

A mutation where the gene product from one allele interferes with the function of the wild-type allele product.

Question 14

Which of the following best describes the mechanism of action for alkylating agents as mutagens?

Accepted Answer

They donate alkyl groups to nucleotide bases, altering base-pairing affinity and often causing transition mutations.

Question 15

Which of the following is a key feature of transposable elements (transposons) in the genome?

Accepted Answer

They can move within and between chromosomes, potentially causing mutations and chromosomal rearrangements.

Question 16

Which of the following best explains why the S O S repair system in E. coli is considered a 'last resort' DNA repair mechanism?

Accepted Answer

It is error-prone and can introduce mutations while allowing replication to continue past DNA damage.

Question 17

Which of the following is a real-world example of a mutagenic exposure that can lead to DNA damage in humans?

Accepted Answer

Medical X-rays, which are a form of ionizing radiation.

Question 18

Which of the following statements about LINEs and SINEs in the human genome is correct?

Accepted Answer

They are types of transposable elements that together make up a significant portion of the human genome.

Question 19

A suppressor mutation can:

Accepted Answer

Relieve or revert the effects of a previous mutation, either within the same gene (intragenic) or elsewhere in the genome (intergenic).

Gene Mutation, DNA Repair, and Transposition: Study Guide

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