Question 1

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid to another in the protein sequence.

Question 2

A patient is found to have a single nucleotide substitution in the coding region of a gene, changing the codon GAA (Glu) to GAG (Glu). What type of mutation is this?

Accepted Answer

Silent mutation

Question 3

Which of the following is a likely consequence of a frameshift mutation?

Accepted Answer

The reading frame of the gene is altered, potentially resulting in a nonfunctional protein.

Question 4

A mutation in a non-coding regulatory region of DNA could have which of the following effects?

Accepted Answer

It may alter the rate of transcription of the gene.

Question 5

Which repair pathway is primarily responsible for removing bulky DNA lesions such as thymine dimers caused by UV light?

Accepted Answer

Nucleotide excision repair

Question 6

A nonsense mutation is best defined as:

Accepted Answer

A mutation that changes a codon to a stop codon, leading to premature termination of translation.

Question 7

Which of the following best describes the principle of PCR (Polymerase Chain Reaction)?

Accepted Answer

It amplifies a specific DNA sequence in vitro using repeated cycles of denaturation, annealing, and extension.

Question 8

A single nucleotide polymorphism (SNP) is defined as:

Accepted Answer

A variation at a single nucleotide position that occurs in more than 1% of the population.

Question 9

Which of the following scenarios is an example of a dominant negative mutation?

Accepted Answer

A mutation that produces a protein interfering with the function of the wild-type protein.

Question 10

A patient with a mutation in the gene responsible for mismatch repair is at increased risk for which of the following conditions?

Accepted Answer

Hereditary nonpolyposis colorectal cancer (HNPCC)

Question 11

Which of the following best explains why mitochondrial DNA is particularly prone to mutations?

Accepted Answer

It is exposed to high levels of reactive oxygen species and has limited repair mechanisms.

Question 12

A frameshift mutation can be caused by which of the following genetic events?

Accepted Answer

Insertion or deletion of nucleotides not in multiples of three

Question 13

Which of the following is a potential effect of a splice-site mutation?

Accepted Answer

Inclusion of introns in the mature mRNA, leading to a nonfunctional protein

Question 14

Which equation correctly represents the number of DNA copies after $$n$$ cycles of PCR, starting from a single DNA molecule?

Accepted Answer

$$N = 2^n$$

Question 15

A mutation that results in the expansion of a trinucleotide repeat is most likely to cause which of the following disorders?

Accepted Answer

Fragile X syndrome

Question 16

Which of the following best describes the function of nonsense-mediated mRNA decay (NMD)?

Accepted Answer

It degrades mRNA transcripts containing premature stop codons to prevent production of truncated proteins.

Question 17

A mutation in a gene's promoter region could most likely result in which of the following?

Accepted Answer

Altered rate of gene transcription

Question 18

Which of the following molecular diagnostic tools is most appropriate for detecting a known point mutation in a gene?

Accepted Answer

Polymerase Chain Reaction (PCR)

Question 19

A patient presents with symptoms of a genetic disorder. DNA sequencing reveals a substitution mutation that changes a codon from GAA (Glu) to UAA (Stop). What is the most likely effect on the protein product?

Accepted Answer

The protein will be truncated and likely nonfunctional.

Question 20

Which of the following best explains why DNA repair pathways are essential for human health?

Accepted Answer

They prevent the accumulation of mutations that can lead to diseases such as cancer.

Gene Mutations: Mechanisms, Effects, and Molecular Diagnostics

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