Question 1

Which enzyme is primarily responsible for unwinding the DNA double helix during replication, and what is the consequence of its activity?

Accepted Answer

Helicase; it creates strain and supercoiling downstream of the replication fork

Question 2

What is the function of single-stranded binding proteins (SSBs) during DNA replication?

Accepted Answer

They prevent separated DNA strands from re-annealing and protect them from nucleases

Question 3

Which of the following best describes the directionality of DNA synthesis by DNA polymerase?

Accepted Answer

DNA polymerase synthesizes DNA in the $5' \rightarrow 3'$ direction

Question 4

What is the role of topoisomerase I during DNA replication?

Accepted Answer

It introduces a single-strand break to allow rotation and relieve supercoiling

Question 5

In prokaryotic DNA replication, what is the significance of having a single origin of replication?

Accepted Answer

It ensures that replication proceeds bidirectionally from one point, efficiently copying the circular genome

Question 6

Why are Okazaki fragments formed during DNA replication?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the $5' \rightarrow 3'$ direction, requiring discontinuous synthesis on the lagging strand

Question 7

Which statement correctly describes the difference between prokaryotic and eukaryotic DNA replication origins?

Accepted Answer

Eukaryotes have multiple origins of replication per chromosome, while prokaryotes typically have a single origin

Question 8

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 9

A mutation in the gene encoding DNA polymerase that prevents it from associating with RNA primers would most directly affect which process?

Accepted Answer

Initiation of DNA strand synthesis

Question 10

Which enzyme is responsible for joining Okazaki fragments together during DNA replication?

Accepted Answer

DNA ligase

Question 11

During DNA replication, which strand is synthesized continuously and why?

Accepted Answer

The leading strand, because DNA polymerase can synthesize in the same direction as the replication fork movement ($5' \rightarrow 3'$)

Question 12

Which of the following best explains why DNA polymerase cannot initiate DNA synthesis on its own?

Accepted Answer

It requires a free $3'$-OH group provided by an RNA primer to add nucleotides

Question 13

A patient is found to have a mutation in topoisomerase II. Which of the following would most likely occur during DNA replication in their cells?

Accepted Answer

Excessive supercoiling would accumulate, potentially stalling replication

Question 14

Which of the following equations correctly represents the energy released during the formation of a phosphodiester bond by DNA polymerase?

Accepted Answer

$dNTP \rightarrow dNMP + PP_i$

Question 15

Which of the following is true regarding the antiparallel nature of DNA replication?

Accepted Answer

The leading strand is synthesized continuously in the $5' \rightarrow 3'$ direction, while the lagging strand is synthesized discontinuously in the $5' \rightarrow 3'$ direction

Question 16

Which of the following would most likely result if single-stranded binding proteins (SSBs) were nonfunctional during DNA replication?

Accepted Answer

The separated DNA strands would re-anneal, preventing proper replication

Question 17

Which of the following best describes the role of topoisomerase II during DNA replication?

Accepted Answer

It introduces a double-strand break at two locations to relieve supercoiling

Question 18

Which of the following is a correct statement about the function of DNA polymerase during replication?

Accepted Answer

It catalyzes the addition of nucleotides to the growing DNA strand using the template strand

Question 19

A researcher observes that DNA replication in a eukaryotic cell is proceeding much slower than normal. Which of the following is the most likely explanation?

Accepted Answer

There are fewer origins of replication active, resulting in longer stretches of DNA being replicated from each origin

DNA Replication: Mechanisms and Enzymes

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