Question 1

Which of the following best describes a frameshift mutation?

Accepted Answer

A mutation that involves the addition or deletion of nucleotides not in multiples of three, shifting the reading frame during translation.

Question 2

A patient is diagnosed with sickle cell disease. Which type of mutation is responsible for this condition?

Accepted Answer

A missense mutation in the hemoglobin beta gene.

Question 3

Which of the following is a consequence of nondisjunction during meiosis?

Accepted Answer

Formation of gametes with abnormal chromosome numbers, leading to aneuploidy.

Question 4

A base substitution changes a codon from $$\mathrm{UCA} ($$serine) to $$\mathrm{UAA} ($$stop). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 5

Which of the following diseases is caused by a trinucleotide repeat expansion?

Accepted Answer

Huntington's disease

Question 6

A mutation occurs in the promoter region of a gene. What is the most likely effect?

Accepted Answer

Change in the amount of protein produced

Question 7

Which of the following best explains why trisomy 21 (Down syndrome) is tolerated in humans, while most other trisomies are lethal?

Accepted Answer

Chromosome 21 contains fewer genes than most other chromosomes.

Question 8

Which of the following is a characteristic of transposable elements?

Accepted Answer

They can move from one location in the genome to another, potentially disrupting gene function.

Question 9

A three-base deletion in the CFTR gene leads to cystic fibrosis. Why does this mutation not cause a frameshift?

Accepted Answer

Because the deletion is a multiple of three, removing one amino acid but preserving the reading frame.

Question 10

Which of the following is true about somatic mutations?

Accepted Answer

They can lead to mosaicism within an individual.

Question 11

A base substitution changes a codon from $$\mathrm{GAA} ($$glutamic acid) to $$\mathrm{GAG} ($$glutamic acid). What type of mutation is this?

Accepted Answer

Silent (synonymous) mutation

Question 12

Which of the following chromosomal rearrangements is most likely to result in gene fusion and cancer, such as the Philadelphia chromosome in chronic myeloid leukemia?

Accepted Answer

Translocation

Question 13

Which of the following is a transition mutation?

Accepted Answer

A purine (A or G) is replaced by another purine.

Question 14

A patient has a mutation in the PAH gene resulting in phenylketonuria. Which metabolic pathway is directly affected?

Accepted Answer

Conversion of phenylalanine to tyrosine

Question 15

Which of the following best describes a pericentric inversion?

Accepted Answer

An inversion that includes the centromere.

Question 16

Which of the following is most likely to occur if a transposon inserts into the coding region of a gene?

Accepted Answer

The gene's function may be disrupted, potentially causing disease.

Question 17

Which of the following is a real-world example of a disease caused by a transposon insertion?

Accepted Answer

Duchenne muscular dystrophy

Question 18

Which of the following best explains why inversions are often 'balanced' and do not result in loss of genetic material?

Accepted Answer

The DNA sequence is rearranged but no genes are deleted or duplicated.

Question 19

A child is born with Turner syndrome. Which chromosomal abnormality is present?

Accepted Answer

Monosomy X (only one X chromosome)

Question 20

Which of the following mechanisms is responsible for nucleotide repeat expansions during DNA replication?

Accepted Answer

Slipped strand mispairing (SSM)

Genetics Study Notes: Mutations, Chromosomal Variation, and Transposable Elements

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