Question 1

During eukaryotic DNA replication, what is the significance of having multiple origins of replication on a linear chromosome?

Accepted Answer

It enables bidirectional replication from several fixed origins, increasing the speed and efficiency of DNA synthesis.

Question 2

Which enzyme is responsible for catalyzing the nucleophilic attack by the 3'-OH group of the primer terminus on the α-phosphate of the incoming dNTP during DNA replication?

Accepted Answer

DNA polymerase

Question 3

What is the role of topoisomerase during DNA replication?

Accepted Answer

It relieves torsional stress caused by DNA unwinding, preventing overwinding of the double helix.

Question 4

Which of the following best describes the synthesis of the lagging strand during DNA replication?

Accepted Answer

It is synthesized discontinuously as Okazaki fragments, which are later joined together.

Question 5

Which activity of DNA polymerase I is essential for the removal of RNA primers during DNA replication?

Accepted Answer

5' to 3' exonuclease activity

Question 6

What is the function of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 7

Which of the following statements about the directionality of DNA synthesis is correct?

Accepted Answer

DNA synthesis occurs in the 5' to 3' direction.

Question 8

What would happen if helicase function was inhibited during DNA replication?

Accepted Answer

DNA strands would not separate, preventing replication fork formation.

Question 9

Which equation correctly represents the formation of a phosphodiester bond during DNA polymerization?

Accepted Answer

$$\mathrm{(dNMP)}_{n} + \mathrm{dNTP} \xrightarrow{DNA\,polymerase} \mathrm{(dNMP)}_{n+1} + PP_i$$

Question 10

In a patient with a mutation that inactivates DNA polymerase I's 5' to 3' exonuclease activity, which process would be most directly affected?

Accepted Answer

Removal of RNA primers from Okazaki fragments

Question 11

Which of the following best explains why DNA replication is considered 'semiconservative'?

Accepted Answer

Each daughter DNA molecule contains one parental strand and one newly synthesized strand.

Question 12

A researcher observes that DNA replication forks in eukaryotic cells advance until they meet another fork traveling in the opposite direction. What does this observation indicate about the nature of eukaryotic DNA replication?

Accepted Answer

Replication is bidirectional from multiple origins.

Question 13

Which protein is responsible for catalyzing the ATP-dependent unwinding of double-stranded DNA during replication?

Accepted Answer

Helicase

Question 14

If topoisomerase activity is inhibited during DNA replication, what is the most likely consequence?

Accepted Answer

Torsional stress will accumulate, leading to overwinding and possible DNA breakage.

Question 15

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

Accepted Answer

A single-stranded binding protein

Question 16

Which process is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 17

A mutation in the gene encoding primase would most likely result in which of the following defects?

Accepted Answer

Inability to synthesize RNA primers, preventing initiation of DNA synthesis

Question 18

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

Accepted Answer

It possesses both 3' to 5' and 5' to 3' exonuclease activities, allowing it to remove RNA primers and proofread DNA.

Question 19

Which of the following best describes the role of single-stranded DNA binding proteins (SSB) at the replication fork?

Accepted Answer

They prevent re-annealing of separated DNA strands, stabilizing single-stranded DNA.

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