Question 1

Which of the following statements best distinguishes a DNA error from a DNA mutation?

Accepted Answer

A DNA error is a mistake made during replication that can be corrected, while a mutation is a change that remains after repair mechanisms fail.

Question 2

DNA polymerase is considered highly accurate, making less than 1 mistake in $$10^9$$ bases. What feature of DNA polymerase is primarily responsible for this accuracy?

Accepted Answer

Its upper exonuclease domain that provides proofreading capacity.

Question 3

The proofreading response of DNA polymerase is most likely triggered by which of the following?

Accepted Answer

The addition of the incorrect nucleotide altering the geometry of the DNA.

Question 4

If DNA polymerase proofreading does not fix an error during replication, what is the most likely outcome?

Accepted Answer

The error will become a permanent mutation in the DNA sequence.

Question 5

Mismatch repair systems further reduce the error rate in DNA replication. If mismatch repair does not fix an error before replication, what happens?

Accepted Answer

The error becomes a mutation in the daughter DNA strand.

Question 6

Which of the following is NOT a type of point mutation?

Accepted Answer

Translocation

Question 7

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

Accepted Answer

An insertion or deletion of nucleotides that alters the reading frame.

Question 8

Which type of DNA damage is most commonly caused by UV light exposure?

Accepted Answer

Cross-linked thymine dimers

Question 9

Base excision repair (BER) is best described as:

Accepted Answer

A process that excises and replaces single damaged bases, often triggered by spontaneous or chemical damage.

Question 10

Which enzyme is responsible for repairing single-stranded breaks in the DNA backbone?

Accepted Answer

DNA ligase

Question 11

A karyotype is used to analyze chromosome-level mutations. Which of the following mutations can be detected using a karyotype?

Accepted Answer

Chromosome inversions, translocations, deletions, and duplications

Question 12

Which of the following statements about DNA damage and mutation is correct?

Accepted Answer

DNA damage refers to physical or chemical changes to DNA, while mutation is a permanent change in the DNA sequence.

Question 13

Which repair mechanism is triggered when major structural kinks occur in the DNA, involving more than one nucleotide?

Accepted Answer

Nucleotide excision repair

Question 14

A patient is exposed to a chemical mutagen that causes single base changes in their DNA. Which repair mechanism is most likely to fix this damage?

Accepted Answer

Base excision repair

Question 15

Which of the following best explains why not all mutations have an impact on the resulting protein or organism?

Accepted Answer

Some mutations are silent, meaning they do not change the amino acid sequence due to redundancy in the genetic code.

Question 16

Which of the following scenarios would most likely result in a nonsense mutation?

Accepted Answer

A base pair substitution that creates a stop codon within a gene.

Question 17

A chromosome translocation is best described as:

Accepted Answer

A broken section of one chromosome becomes attached to another chromosome.

Question 18

If a cell experiences a double-stranded break in its DNA, which of the following is true regarding repair?

Accepted Answer

Repairing double-stranded breaks requires more machinery and may not always restore the original sequence.

Question 19

Which of the following is a real-world example of a mutation caused by chromosome-level abnormalities?

Accepted Answer

Trisomy 21, which results from an extra copy of chromosome 21.

DNA Errors, Repair, and Mutation: Mechanisms and Impact

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