Question 1

Which of the following best describes a missense mutation?

Accepted Answer

A base-pair change that results in the substitution of one amino acid for another in the protein sequence.

Question 2

A mutation that occurs in a promoter region most likely affects which of the following?

Accepted Answer

The efficiency or amount of transcription of the gene.

Question 3

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

Accepted Answer

Guanine (G) replaced by Adenine (A)

Question 4

A frameshift mutation is most likely to result from which of the following events?

Accepted Answer

Insertion or deletion of one or more base pairs not in multiples of three

Question 5

Which of the following best explains why dominant mutations are easier to detect than recessive mutations?

Accepted Answer

Dominant mutations manifest in the phenotype with only one mutant allele present.

Question 6

A mutation that creates a new splice site within an intron, leading to the inclusion of additional nucleotides in the mature mRNA, is called:

Accepted Answer

A cryptic splice site mutation

Question 7

Which of the following is a likely consequence of a mutation in the polyadenylation signal sequence ($$5'\ \mathrm{AAUAAA}\ 3') of a $$gene?

Accepted Answer

Blockage of proper 3' processing of mRNA, leading to reduced protein production

Question 8

Which of the following best describes a second-site reversion (suppressor mutation)?

Accepted Answer

A mutation in a different gene that compensates for the original mutation, restoring the wild-type phenotype

Question 9

Which of the following is a common result of DNA strand slippage during replication in regions with repeat sequences?

Accepted Answer

Expansion or contraction of the number of repeats

Question 10

A patient is diagnosed with a trinucleotide repeat disorder. Which of the following best explains the molecular basis of this disease?

Accepted Answer

Expansion of a specific trinucleotide sequence beyond a threshold, disrupting gene function

Question 11

Which of the following is the most common spontaneous mutation mechanism during DNA replication?

Accepted Answer

Tautomeric shifts leading to base-pair mismatches

Question 12

Depurination results in which of the following DNA lesions?

Accepted Answer

A site lacking a purine base (apurinic site)

Question 13

Which of the following chemical mutagens acts as a nucleotide base analog and can cause transition mutations?

Accepted Answer

2-Aminopurine

Question 14

The Ames test is used to:

Accepted Answer

Assess the mutagenic potential of chemical compounds by measuring reversion rates in bacteria

Question 15

A mutation in the gene encoding the tumor suppressor p53 is most likely to result in:

Accepted Answer

Increased susceptibility to cancer

Question 16

Which DNA repair mechanism is responsible for removing and replacing mismatched bases that escape proofreading during replication?

Accepted Answer

Mismatch repair

Question 17

A mutation that changes a codon from UAU (tyrosine) to UAA (stop) is classified as:

Accepted Answer

Nonsense mutation

Question 18

Which of the following best describes a germ-line mutation?

Accepted Answer

A mutation that occurs in cells giving rise to gametes and can be passed to offspring

Question 19

Which of the following is a likely outcome of a splicing mutation at the 5' GU or 3' AG site of an intron?

Accepted Answer

Retention of the intron sequence in the mature mRNA

Question 20

Which of the following statements about mutation hotspots is correct?

Accepted Answer

Mutation hotspots are often associated with large gene size and increased mutation frequency.

Genetic Mutations: Mechanisms, Types, and Consequences

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