Question 1

Which model of DNA replication was supported by the results of the Meselson-Stahl experiment after one generation in 14N medium?

Accepted Answer

Semiconservative model

Question 2

During DNA replication, which enzyme is responsible for synthesizing the RNA primer required for DNA polymerase to begin synthesis?

Accepted Answer

Primase

Question 3

In E. coli, what is the function of the DnaA protein during the initiation of DNA replication?

Accepted Answer

It binds to DnaA boxes at the origin of replication to initiate DNA strand separation

Question 4

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

Accepted Answer

5' to 3' direction

Question 5

What is the main reason DNA replication is highly accurate?

Accepted Answer

Proofreading activity of DNA polymerase and induced fit mechanism

Question 6

Which enzyme is responsible for removing RNA primers and replacing them with DNA in E. coli?

Accepted Answer

DNA polymerase I

Question 7

Why is DNA ligase required during DNA replication?

Accepted Answer

To join Okazaki fragments on the lagging strand

Question 8

Which of the following statements about eukaryotic DNA replication is correct?

Accepted Answer

Eukaryotes have multiple origins of replication per chromosome

Question 9

What is the 'end replication problem' in eukaryotic cells?

Accepted Answer

DNA polymerase cannot fully replicate the 5' ends of linear chromosomes, leading to progressive shortening

Question 10

Which enzyme solves the end replication problem by extending the 3' overhang of linear chromosomes?

Accepted Answer

Telomerase

Question 11

A mutation in the gene encoding the sliding clamp (β subunit) of DNA polymerase III in E. coli would most likely result in which of the following?

Accepted Answer

Decreased processivity of DNA polymerase III

Question 12

Which of the following best explains why cancer cells can divide indefinitely?

Accepted Answer

They retain telomerase activity, maintaining telomere length

Question 13

During DNA replication, which of the following reactions provides the energy for the formation of the phosphodiester bond?

Accepted Answer

Release of pyrophosphate (PPi) from the incoming dNTP

Question 14

Which of the following is a function of the 3' to 5' exonuclease activity of DNA polymerase?

Accepted Answer

Proofreading and removal of mismatched nucleotides

Question 15

A patient is found to have a mutation that inactivates the gene for DNA helicase. Which of the following would most likely be observed in their cells?

Accepted Answer

Failure to separate the two DNA strands at the origin of replication

Question 16

Which of the following best describes the role of the AT-rich region at the origin of replication in E. coli?

Accepted Answer

It is easier to separate due to fewer hydrogen bonds, facilitating DNA strand separation

Question 17

Which of the following equations correctly represents the chemical reaction catalyzed by DNA polymerase during DNA synthesis?

Accepted Answer

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

Question 18

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized discontinuously on the lagging strand

Question 19

In the Meselson-Stahl experiment, what would be the expected result after two generations in 14N medium if DNA replication were dispersive?

Accepted Answer

One intermediate band

Question 20

Which of the following is a direct consequence of the inability of DNA polymerase to initiate synthesis de novo (without a primer)?

Accepted Answer

The requirement for primase to synthesize an RNA primer

DNA Replication: Mechanisms, Enzymes, and Regulation

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