Question 1

Which of the following best describes a frameshift mutation and its likely consequence on a protein-coding gene?

Accepted Answer

An insertion or deletion of nucleotides that alters the reading frame, potentially resulting in a completely different 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 chemical mutagen acts by inserting itself between DNA base pairs, causing distortions and potential frameshift mutations?

Accepted Answer

Ethidium bromide, an intercalating agent.

Question 6

A DNA repair system that uses the methylation status of DNA to distinguish the newly synthesized strand from the template strand is known as:

Accepted Answer

Mismatch repair.

Question 7

Which of the following best explains why individuals with xeroderma pigmentosum (XP) are highly sensitive to sunlight and have a greatly increased risk of skin cancer?

Accepted Answer

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

Question 8

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

Accepted Answer

Huntington disease.

Question 9

A mutagenic chemical that can substitute for a normal DNA base during replication, increasing the frequency of tautomeric shifts, is called:

Accepted Answer

A base analog.

Question 10

Which DNA repair mechanism is unique in that it directly reverses the formation of thymine dimers using visible light?

Accepted Answer

Photoreactivation repair.

Question 11

A researcher uses the Ames test to evaluate a new industrial chemical. What is the principle behind this test?

Accepted Answer

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

Question 12

Which of the following best describes the action of alkylating agents on DNA?

Accepted Answer

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

Question 13

Which of the following is a likely consequence of a double-strand break in DNA if not properly repaired?

Accepted Answer

Chromosomal rearrangements, cancer, or cell death.

Question 14

Which repair pathway is most likely to be error-prone and is considered a 'last resort' in bacteria to allow survival after extensive DNA damage?

Accepted Answer

SOS repair system.

Question 15

A mutation in a gene results in a protein with a new or enhanced function. This is best described as:

Accepted Answer

A gain-of-function mutation.

Question 16

Which of the following best explains why tandemly repeated sequences are considered 'hot spots' for DNA mutation?

Accepted Answer

Replication slippage is more likely to occur, leading to insertions or deletions.

Question 17

Which of the following is a correct description of a suppressor mutation?

Accepted Answer

A second mutation that relieves or reverts the effects of a previous mutation.

Question 18

Which of the following statements about transposable elements in the human genome is correct?

Accepted Answer

LINEs and SINEs make up a significant portion of the human genome and are types of transposable elements.

Question 19

A patient with Cockayne syndrome exhibits developmental and neurological conditions, sunlight sensitivity, but no increase in cancer risk. This is due to a defect in which DNA repair pathway?

Accepted Answer

Nucleotide excision repair (NER).

Question 20

Which of the following best describes the process of homologous recombination repair of double-strand breaks?

Accepted Answer

It uses a homologous sequence, usually on a sister chromatid, to accurately repair the break.

Gene Mutation, DNA Repair, and Transposition: Study Notes for Genetics

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