Question 1

Which of the following best describes a frameshift mutation, and what is its most likely effect on the resulting protein?

Accepted Answer

An insertion or deletion of bases not in multiples of three; likely causes a shift in the reading frame and a nonfunctional protein.

Question 2

A mutation changes the codon GAA (glutamic acid) to GAG (also glutamic acid). What type of mutation is this, and why?

Accepted Answer

Silent mutation; the amino acid remains the same due to the degeneracy of the genetic code.

Question 3

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

Accepted Answer

RNA polymerases lack proofreading activity, 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 which genetic phenomenon?

Accepted Answer

Haploinsufficiency

Question 5

Which DNA repair mechanism is responsible for correcting mismatches that escape proofreading during DNA replication?

Accepted Answer

Mismatch repair

Question 6

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

Accepted Answer

Nonsense mutation; results in premature termination of translation.

Question 7

Which of the following is a consequence of phosphorylation of eIF2α during cellular stress?

Accepted Answer

Inhibition of translation initiation, conserving cellular resources

Question 8

A base analog such as 5-bromouracil can cause mutations by:

Accepted Answer

Mimicking normal bases and pairing incorrectly during replication

Question 9

Which of the following best describes a dominant negative mutation?

Accepted Answer

A mutation that results in a nonfunctional protein that interferes with the function of the wild-type protein

Question 10

Which of the following is a transition mutation?

Accepted Answer

$$A \rightarrow G$$

Question 11

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

Accepted Answer

The redundancy (degeneracy) of the genetic code and the wobble hypothesis

Question 12

Which of the following mutagens is most likely to cause frameshift mutations?

Accepted Answer

Intercalating agents such as acridine orange

Question 13

Which of the following best describes the effect of a nonsense mutation?

Accepted Answer

It changes an amino acid codon to a stop codon, resulting in a truncated protein.

Question 14

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

Accepted Answer

Huntington’s disease, caused by an expanded CAG repeat in the HTT gene

Question 15

Which of the following statements about spontaneous mutations is correct?

Accepted Answer

They arise from normal biological or chemical processes and are random events.

Question 16

Which of the following best explains why larger genomes have a higher total number of mutations per generation, even though their per-base mutation rate is lower?

Accepted Answer

Larger genomes have more DNA bases, so even with a lower per-base mutation rate, the total number of mutations per genome is higher.

Question 17

Which of the following is a likely consequence of a mutation that introduces a thymine dimer in DNA?

Accepted Answer

Distortion of the DNA helix, potentially blocking replication or causing error-prone repair

Question 18

A mutation changes a codon from GAG (glutamic acid) to GTG (valine). This is an example of which type of mutation?

Accepted Answer

Missense mutation (non-conservative)

Question 19

Which of the following best describes the role of ubiquitination in gene regulation?

Accepted Answer

It targets proteins for degradation by the proteasome, regulating protein stability and signaling pathways.

Question 20

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

Accepted Answer

One daughter cell will inherit a permanent mutation, while the other will be wild-type.

Mutations, DNA Repair, and Their Impact on Gene Expression

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