Question 1

Which of the following best describes a transition mutation?

Accepted Answer

A purine is replaced by another purine, or a pyrimidine is replaced by another pyrimidine.

Question 2

A mutation changes the codon UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 3

Which DNA repair mechanism is responsible for removing uracil from DNA and replacing it with cytosine?

Accepted Answer

Base excision repair (BER)

Question 4

A patient is diagnosed with Huntington disease, which is caused by an expansion of CAG repeats. This is an example of which type of mutation?

Accepted Answer

Trinucleotide repeat expansion

Question 5

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

Accepted Answer

It uses mutant Salmonella typhimurium strains to detect reversion mutations.

Question 6

Which of the following best explains why frameshift mutations are often more deleterious than point mutations?

Accepted Answer

They change the reading frame, potentially altering every amino acid downstream.

Question 7

Which repair mechanism distinguishes the newly synthesized DNA strand from the template strand by methylation?

Accepted Answer

Mismatch repair (MMR)

Question 8

A chemical mutagen causes the deamination of cytosine. What is the resulting base, and what type of mutation can this cause?

Accepted Answer

Uracil; transition mutation

Question 9

Which of the following is a consequence of nonhomologous end joining (NHEJ) in double-strand break repair?

Accepted Answer

Direct ligation of broken DNA ends, often resulting in mutations

Question 10

Which of the following best describes the role of the p53 protein in response to DNA damage?

Accepted Answer

It acts as a transcription factor to pause the cell cycle or induce apoptosis.

Question 11

A mutation in the promoter region of a gene most likely results in which of the following?

Accepted Answer

Altered levels of gene expression

Question 12

Which of the following is a property of a base analog such as 5-bromodeoxyuridine (BrdU)?

Accepted Answer

It can be incorporated into DNA in place of thymine and pair with guanine.

Question 13

Which of the following best explains why not all indels (insertions or deletions) cause frameshift mutations?

Accepted Answer

Indels that are multiples of three nucleotides do not shift the reading frame.

Question 14

Which of the following is a likely outcome of a tautomeric shift during DNA replication?

Accepted Answer

A transition mutation due to abnormal base pairing

Question 15

Which of the following best describes the process of gene conversion during homologous recombination?

Accepted Answer

One allele is converted to another due to mismatch repair in heteroduplex DNA.

Question 16

Which of the following is a direct result of exposure to UV light on DNA?

Accepted Answer

Formation of pyrimidine dimers

Question 17

A patient is exposed to X-rays, resulting in a double-strand break in DNA. Which repair pathway is most likely to result in error-free repair if a sister chromatid is available?

Accepted Answer

Synthesis-dependent strand annealing (SDSA)

Question 18

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

Accepted Answer

It is a second mutation that compensates for the effects of a previous mutation.

Question 19

Which of the following best describes the function of DNA glycosylase in base excision repair?

Accepted Answer

It removes damaged or incorrect bases, creating an apurinic/apyrimidinic site.

Chapter 10

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