Question 1

Which of the following best describes the directionality of eukaryotic DNA replication on a linear chromosome?

Accepted Answer

It is bidirectional and proceeds from several fixed origins.

Question 2

During DNA replication, what is the primary function of helicase?

Accepted Answer

To catalyze the ATP-dependent unwinding of double-stranded DNA.

Question 3

Which enzyme is responsible for relieving the torsional stress generated ahead of the replication fork during DNA unwinding?

Accepted Answer

Topoisomerase

Question 4

What is the chemical reaction catalyzed by DNA polymerase during DNA synthesis?

Accepted Answer

Nucleophilic attack by the 3'-OH of the primer terminus on the $$\alpha-$$phosphate of the incoming dNTP, forming a phosphodiester bond and releasing pyrophosphate.

Question 5

Which of the following statements about DNA polymerase I is correct?

Accepted Answer

It has both 3' to 5' and 5' to 3' exonuclease activities in addition to polymerase activity.

Question 6

In the context of lagging strand synthesis during DNA replication, which of the following sequences of events is correct?

Accepted Answer

Primase synthesizes RNA primers, DNA polymerase synthesizes Okazaki fragments, DNA polymerase I removes RNA primers and fills gaps, DNA ligase seals nicks.

Question 7

Which of the following is a direct consequence if topoisomerase activity is inhibited during DNA replication?

Accepted Answer

DNA strands become overwound ahead of the replication fork, stalling replication.

Question 8

Which of the following best explains why eukaryotic chromosomes have multiple origins of replication?

Accepted Answer

Because eukaryotic chromosomes are much larger and require multiple starting points to complete replication efficiently during S phase.

Question 9

Which of the following is NOT a requirement for DNA polymerase activity?

Accepted Answer

A supply of ribonucleoside triphosphates (rNTPs)

Question 10

A mutation in the gene encoding primase would most directly affect which step of DNA replication?

Accepted Answer

The synthesis of RNA primers required for DNA polymerase to initiate DNA synthesis

Question 11

Which of the following best describes the role of DNA polymerase I in the removal of RNA primers during DNA replication?

Accepted Answer

It removes RNA primers using its 5' to 3' exonuclease activity and replaces them with DNA.

Question 12

Which of the following statements about the replication fork is correct?

Accepted Answer

Both the leading and lagging strands are synthesized in the 5' to 3' direction.

Question 13

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

Because the lagging strand template is oriented 5' to 3', requiring discontinuous synthesis in short fragments.

Question 14

A patient is treated with a drug that inhibits DNA ligase. Which of the following outcomes would you expect during DNA replication?

Accepted Answer

Okazaki fragments on the lagging strand remain unjoined, resulting in nicks in the DNA.

Question 15

Which of the following is the correct sequence of events at a eukaryotic replication origin during S phase?

Accepted Answer

Origin recognition, helicase loading, DNA unwinding, primer synthesis, DNA synthesis

DNA Replication, Transcription, and Translation in Eukaryotes

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