Question 1

Which of the following best describes the role of DNA polymerase during DNA replication?

Accepted Answer

It synthesizes new DNA strands by adding nucleotides to a pre-existing chain and proofreads for errors.

Question 2

A patient is exposed to high levels of ultraviolet (UV) radiation. Which specific DNA damage is most likely to occur, and what repair mechanism is primarily responsible for fixing it?

Accepted Answer

Formation of thymine dimers; repaired by nucleotide excision repair.

Question 3

During DNA replication, what is the consequence if a mismatched base is not corrected by DNA polymerase proofreading?

Accepted Answer

A permanent mutation may be established in the daughter DNA strand.

Question 4

Which enzyme is responsible for joining the newly synthesized DNA fragments during lagging strand synthesis?

Accepted Answer

DNA ligase

Question 5

A scientist observes that after DNA replication, a segment of DNA contains a mismatched base pair. Which sequence of events correctly describes how mismatch repair fixes this error?

Accepted Answer

Mismatch repair enzymes recognize the mismatch, remove a section of the newly synthesized strand, DNA polymerase fills in the correct bases, and DNA ligase seals the strand.

Question 6

Which of the following best explains why DNA replication has a very low error rate (about one mistake in $$1 	imes 10^9$ base pairs)?

Accepted Answer

Proofreading by DNA polymerase and post-replication mismatch repair together correct most errors.

Question 7

Which of the following is NOT a step in the nucleotide excision repair pathway?

Accepted Answer

Primase synthesizes a new RNA primer at the site of damage.

Question 8

If a DNA polymerase incorporates an incorrect nucleotide, what is the sequence of events that allows for correction during replication?

Accepted Answer

The shape distortion causes polymerization to stop, the 3' end shifts to the exonuclease site, the incorrect nucleotide is removed, and synthesis resumes.

Question 9

Which of the following best describes the function of topoisomerase during DNA replication?

Accepted Answer

It breaks and rejoins DNA strands to relieve tension caused by unwinding.

Question 10

A mutation in the gene encoding DNA ligase would most likely result in which of the following cellular consequences?

Accepted Answer

Accumulation of unjoined DNA fragments, especially on the lagging strand.

Question 11

Which of the following scenarios would most likely lead to a permanent mutation in a cell's DNA?

Accepted Answer

A thymine dimer is formed and not repaired before the next round of DNA replication.

Question 12

Which of the following best explains why DNA damage can affect one or both strands of the DNA double helix?

Accepted Answer

Some damaging agents, such as UV light, cause covalent bonds between bases on the same strand, while others, like X-rays, can break both strands.

Question 13

Which of the following is a direct result of the proofreading activity of DNA polymerase?

Accepted Answer

Decreased frequency of permanent mutations in the genome.

Question 14

A cell is exposed to a chemical that inhibits the function of mismatch repair enzymes. What is the most likely outcome?

Accepted Answer

Increased accumulation of replication errors after DNA synthesis.

Question 15

Which of the following steps occurs first during the process of DNA replication?

Accepted Answer

Helicase unwinds the DNA double helix.

Question 16

Which of the following best describes the difference between proofreading and mismatch repair?

Accepted Answer

Proofreading occurs during DNA synthesis, while mismatch repair occurs after DNA synthesis.

Question 17

Which of the following is the correct order of events in nucleotide excision repair?

Accepted Answer

Error detection, DNA unwinding, nucleotide excision, DNA synthesis, strand ligation

Question 18

If a cell's DNA polymerase loses its exonuclease activity, what is the most likely effect on DNA replication?

Accepted Answer

The error rate during DNA replication will increase significantly.

Question 19

Which of the following best explains why DNA ligase is essential for lagging strand synthesis?

Accepted Answer

It joins the short DNA fragments (Okazaki fragments) into a continuous strand.

Question 20

A researcher finds that a cell has a high frequency of mutations specifically at sites of UV-induced thymine dimers. Which repair pathway is most likely defective in this cell?

Accepted Answer

Nucleotide excision repair

Week 8 - Oct 31

Study Guide - Practice Questions

Study Guide - Flashcards