Question 1

Which of the following best describes the molecular change that causes sickle-cell anemia?

Accepted Answer

A point mutation resulting in a missense mutation in the β-globin gene

Question 2

A DNA sequence 3'-TACTTGTCCGATATC-5' is mutated to 3'-TACTTGTCCAATATC-5'. Using the genetic code, what type of mutation is this?

Accepted Answer

Point mutation

Question 3

Which of the following mutations is most likely to result in a nonfunctional protein product?

Accepted Answer

A base-pair deletion in the middle of a coding sequence

Question 4

Which of the following best explains why silent mutations do not affect the protein sequence?

Accepted Answer

The genetic code is redundant, so multiple codons can code for the same amino acid.

Question 5

A DNA template strand has the sequence 3'-C T T-5'. The corresponding mRNA codon is 5'-G A A-3'. If this codon is mutated to 5'-G U A-3', what amino acid change occurs?

Accepted Answer

Glutamate (Glu) to Valine (Val)

Question 6

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

Accepted Answer

A premature stop codon is introduced, leading to a truncated protein.

Question 7

Which repair mechanism is responsible for removing pyrimidine dimers caused by UV radiation?

Accepted Answer

Nucleotide excision repair

Question 8

What is the effect of intercalating agents on DNA?

Accepted Answer

They distort the DNA helix, leading to errors during replication and transcription.

Question 9

Which of the following best explains why individuals with sickle-cell disease are resistant to malaria?

Accepted Answer

The altered hemoglobin impairs the malaria parasite's ability to infect red blood cells.

Question 10

A person has a 32-base-pair deletion in the CCR5 gene, resulting in a nonfunctional receptor. What is the likely consequence?

Accepted Answer

Resistance to HIV infection

Question 11

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

Accepted Answer

A single nucleotide change that results in a different amino acid in the protein sequence

Question 12

Which of the following best describes the role of DNA ligase in DNA repair?

Accepted Answer

It joins the sugar-phosphate backbone after new DNA is synthesized.

Question 13

Ionizing radiation, such as X-rays, can cause which of the following types of DNA damage?

Accepted Answer

Double and single strand breaks

Question 14

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

Accepted Answer

Nonsense mutation

Question 15

Which of the following is a potential benefit of a genetic mutation?

Accepted Answer

Increased resistance to infectious diseases

Question 16

A DNA sequence is mutated from 3'-AGGATGCCGCGC-5' to 3'-AGGATAATGCCGCGC-5'. What type of mutation is this?

Accepted Answer

Insertion with frameshift

Question 17

Which of the following is NOT a possible cause of DNA mutation?

Accepted Answer

DNA ligase activity

Question 18

Which of the following best describes a frameshift mutation?

Accepted Answer

An insertion or deletion that alters the reading frame of the gene

Question 19

Which of the following is a real-life example of a mutation that provides a selective advantage?

Accepted Answer

CCR5 Δ32 mutation conferring resistance to HIV

Question 20

Which of the following statements about DNA proofreading and repair is correct?

Accepted Answer

DNA repair systems reduce the frequency of mutations by correcting errors.

Mutations: Types, Mechanisms, and Biological Consequences

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