Question 1

Which of the following statements best describes the role of DnaA-ATP in bacterial DNA replication initiation at oriC?

Accepted Answer

DnaA-ATP binds to short repeated sequences, forming an oligomeric complex that melts the DNA at the origin.

Question 2

In bacterial DNA replication, why must the oriC region be fully methylated before initiation can occur?

Accepted Answer

Methylation allows recognition proteins to distinguish old template from new DNA.

Question 3

Which of the following is a direct consequence of the ATPase activity of DnaA during replication initiation?

Accepted Answer

DnaA is inactivated by converting ATP to ADP, preventing further initiation.

Question 4

Which protein is responsible for unwinding the DNA double helix at the replication fork in bacteria?

Accepted Answer

DnaB

Question 5

What is the function of DNA gyrase during bacterial DNA replication?

Accepted Answer

It relieves supercoiling ahead of the replication fork.

Question 6

In eukaryotic DNA replication, what is the role of the Origin Recognition Complex (ORC)?

Accepted Answer

It binds to the ARS consensus sequence to mark the origin for replication.

Question 7

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

Accepted Answer

Multiple origins allow the large eukaryotic genome to be replicated quickly during S phase.

Question 8

Which of the following statements about the ARS (Autonomously Replicating Sequence) in yeast is correct?

Accepted Answer

ARS contains a consensus sequence that is essential, but additional elements are required for full function.

Question 9

A temperature-sensitive mutant in a bacterial replication protein shows immediate cessation of cell growth when shifted to a non-permissive temperature. Which stage of replication is most likely affected?

Accepted Answer

Initiation stage, because defects here prevent the start of new replication cycles.

Question 10

Which of the following is a key difference between bacterial and eukaryotic DNA replication initiation?

Accepted Answer

Eukaryotic replication involves a two-step process of licensing and firing, while bacterial replication does not.

Question 11

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

Accepted Answer

$$dNTP + (DNA)_{n} \rightarrow (DNA)_{n+1} + PP_i$$

Question 12

Which of the following best describes the processivity of DNA polymerase?

Accepted Answer

The ability of DNA polymerase to synthesize DNA without dissociating from the template.

Question 13

During eukaryotic DNA replication, which factor is responsible for activating the MCM helicase and converting the pre-replication complex to the pre-initiation complex?

Accepted Answer

DDK (Dbf4-dependent kinase)

Question 14

Which of the following is a function of single-strand binding proteins during DNA replication?

Accepted Answer

They stabilize unwound DNA to prevent re-annealing.

Question 15

A mutation in a bacterial DNA polymerase that eliminates its 3'-5' exonuclease activity would most likely result in which phenotype?

Accepted Answer

Decreased fidelity of DNA replication due to loss of proofreading.

Question 16

Which of the following best explains why replicons near one another in eukaryotic chromosomes tend to be activated at similar times?

Accepted Answer

They are located in regions of active chromatin that are accessible to replication machinery.

Question 17

Which of the following is true regarding the minimal origin of replication in E. coli?

Accepted Answer

It is defined by the distance between the outside members of the 13-mer and 9-mer repeats.

Question 18

Which of the following is a correct statement about temperature-sensitive mutants in bacterial DNA replication?

Accepted Answer

At the non-permissive temperature, the mutant protein loses function, revealing the mutant phenotype.

Question 19

Which of the following is NOT a function of DNA polymerases in bacteria?

Accepted Answer

Unwinding the DNA double helix

DNA Replication: Mechanisms and Regulation in Prokaryotes and Eukaryotes

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