Question 1

Which of the following best describes the role of DNA polymerase III during DNA replication in E. coli?

Accepted Answer

It adds nucleotides to the 3' end of a growing DNA strand during elongation.

Question 2

During DNA replication, which enzyme is responsible for relieving the tension caused by unwinding of the DNA double helix?

Accepted Answer

Topoisomerase

Question 3

If a DNA strand has the sequence 5'-ATGCCGTA-3', what is the complementary strand produced during replication?

Accepted Answer

3'-TACGGCAT-5'

Question 4

Which of the following statements about the leading and lagging strands during DNA replication is correct?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments called Okazaki fragments.

Question 5

Which enzyme joins Okazaki fragments together during DNA replication?

Accepted Answer

DNA ligase

Question 6

What is the main reason why the end-replication problem occurs in eukaryotes but not in prokaryotes?

Accepted Answer

Eukaryotes have linear chromosomes, so the ends cannot be fully replicated by DNA polymerase.

Question 7

Which of the following best describes the function of telomerase?

Accepted Answer

It extends the 3' end of linear chromosomes by adding repetitive DNA sequences.

Question 8

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

Accepted Answer

Accumulation of unjoined Okazaki fragments on the lagging strand.

Question 9

Which of the following equations correctly represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 10

During proofreading, DNA polymerase detects and corrects mismatched nucleotides. Which property of DNA polymerase allows this function?

Accepted Answer

Its 3' to 5' exonuclease activity.

Question 11

A patient’s cells show rapid chromosome shortening and early cell death. Which enzyme is most likely deficient?

Accepted Answer

Telomerase

Question 12

Which of the following best explains why DNA polymerase requires a primer to begin synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' hydroxyl group.

Question 13

Which of the following mechanisms is NOT involved in DNA damage repair?

Accepted Answer

DNA methylation

Question 14

Which of the following is a consequence of the end-replication problem if left unresolved?

Accepted Answer

Chromosome ends become shorter, potentially leading to loss of genetic information.

Question 15

Which of the following best describes the composition of telomeres?

Accepted Answer

Short, repetitive DNA sequences at the ends of linear chromosomes.

Question 16

Which enzyme synthesizes the short RNA primer required for DNA replication?

Accepted Answer

Primase

Question 17

A scientist observes that DNA replication in a cell is proceeding very slowly and there is a buildup of supercoiled DNA ahead of the replication fork. Which enzyme is most likely malfunctioning?

Accepted Answer

Topoisomerase

Question 18

Which of the following is the correct order of events during DNA replication on the lagging strand?

Accepted Answer

Primase synthesizes RNA primer, DNA polymerase III extends DNA, DNA ligase joins fragments.

Question 19

Which of the following best explains why telomerase is only active in certain cell types?

Accepted Answer

Telomerase activity is restricted to cells that divide frequently, such as stem cells and germ cells.

DNA Replication: Mechanisms, Enzymes, and Repair

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