Question 1

Which of the following best describes a frameshift mutation and its likely consequence on protein synthesis?

Accepted Answer

An insertion or deletion of nucleotides not in multiples of three, causing a shift in the reading frame and likely resulting in a nonfunctional protein.

Question 2

A mutation changes a codon from GAA (glutamic acid) to GUA (valine). What type of mutation is this, and what is its likely effect?

Accepted Answer

Non-conservative missense mutation; likely to disrupt protein function due to a change in amino acid properties.

Question 3

Which of the following best explains why RNA viruses, such as HIV, evolve more rapidly than DNA viruses?

Accepted Answer

RNA viruses lack proofreading mechanisms, resulting in higher mutation rates.

Question 4

A patient with Marfan syndrome has one mutated and one normal allele of the FBN1 gene. This is an example of:

Accepted Answer

Haploinsufficiency

Question 5

Which of the following DNA repair mechanisms specifically corrects errors that escape proofreading during DNA replication?

Accepted Answer

Mismatch repair

Question 6

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

Accepted Answer

Nonsense mutation; results in premature termination of translation.

Question 7

Which of the following best describes the 'wobble' hypothesis in tRNA-codon pairing?

Accepted Answer

The third base of the codon can pair with multiple bases in the tRNA anticodon, allowing one tRNA to recognize several codons.

Question 8

Which of the following is a likely consequence of a dominant negative mutation in the p53 tumor suppressor gene?

Accepted Answer

The mutant p53 protein interferes with the function of the wild-type protein, leading to loss of tumor suppressor activity.

Question 9

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 10

Which of the following mutagens is most likely to cause thymine dimers in DNA?

Accepted Answer

Ultraviolet (UV) light

Question 11

A mutation in the third position of a codon often does not change the encoded amino acid. This is due to:

Accepted Answer

The degeneracy of the genetic code and wobble base pairing.

Question 12

Which of the following best explains why a silent mutation can still affect gene expression?

Accepted Answer

It can alter mRNA stability, translation efficiency, or splicing even if the amino acid sequence is unchanged.

Question 13

Which of the following is a real-life example of a disease caused by a dominant negative mutation?

Accepted Answer

Collagen disorders affecting the triple helix structure

Question 14

Which of the following best describes the effect of phosphorylation of eIF2α during cellular stress?

Accepted Answer

It blocks translation initiation, reducing overall protein synthesis.

Question 15

A DNA sequence undergoes deamination, converting cytosine to uracil. If unrepaired, what is the most likely outcome after DNA replication?

Accepted Answer

A transition mutation, with a C-G pair replaced by a T-A pair.

Question 16

Which of the following best describes the process by which proteins destined for secretion are targeted to the endoplasmic reticulum (ER)?

Accepted Answer

They contain an N-terminal signal sequence recognized by the signal recognition particle (SRP), which directs the ribosome to the ER membrane.

Question 17

Which of the following is a likely effect of a loss-of-function mutation in a tumor suppressor gene?

Accepted Answer

Increased cell proliferation and risk of cancer.

Question 18

Which of the following best describes the difference between antigenic drift and antigenic shift in viruses?

Accepted Answer

Antigenic drift involves small mutations over time; antigenic shift involves major changes due to reassortment of genome segments.

Question 19

Which of the following is a likely outcome if a DNA mismatch is not repaired before the next round of replication?

Accepted Answer

One daughter cell will have the mutation, and the other will be wild-type.

Mutations and DNA Repair: Mechanisms, Types, and Effects

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