Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one newly synthesized strand.

Question 2

During DNA replication in E. coli, what is the role of the sliding clamp (β subunit) in DNA polymerase III?

Accepted Answer

It keeps DNA polymerase bound to the template, allowing for processive DNA synthesis.

Question 3

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

Accepted Answer

Topoisomerase

Question 4

What is the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments by forming phosphodiester bonds between adjacent nucleotides.

Question 5

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

Accepted Answer

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

Question 6

In eukaryotic cells, what problem arises during the replication of linear chromosomes, and how is it solved?

Accepted Answer

The 5' end cannot be replicated, solved by telomerase extending telomeric DNA.

Question 7

Which activity of DNA polymerase I is responsible for removing RNA primers during DNA replication?

Accepted Answer

5'-exonuclease activity

Question 8

A patient is diagnosed with Huntington’s disease, which is associated with an increased number of CAG repeats in the huntingtin gene. What is the molecular mechanism that most likely leads to this increase during DNA replication?

Accepted Answer

Polymerase slippage resulting in loop formation and repeat expansion

Question 9

Which of the following best explains why RNA viruses have higher mutation rates compared to DNA viruses?

Accepted Answer

RNA-dependent RNA polymerases lack proofreading activity.

Question 10

During DNA replication, which enzyme catalyzes the formation of a new phosphodiester bond between nucleotides?

Accepted Answer

DNA polymerase

Question 11

Which of the following equations correctly represents the DNA polymerase reaction for chain elongation?

Accepted Answer

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

Question 12

A mutation in the clamp loader protein of E. coli would most likely result in which of the following?

Accepted Answer

Reduced processivity of DNA polymerase III due to inability to load the sliding clamp

Question 13

Which of the following is a direct consequence of dNTP pool imbalance during DNA replication?

Accepted Answer

Higher rates of misincorporation and mutation

Question 14

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

Accepted Answer

Helicase

Question 15

In the two-metal ion mechanism of DNA polymerase, what is the primary role of the metal ions?

Accepted Answer

To coordinate substrates and stabilize the transition state during phosphodiester bond formation

Question 16

Which of the following best describes the process of 'nick translation' during DNA replication?

Accepted Answer

DNA polymerase I removes RNA primers and replaces them with DNA using its 5'-exonuclease and polymerase activities.

Question 17

Which of the following is a key difference between prokaryotic and eukaryotic DNA replication origins?

Accepted Answer

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

Question 18

Which of the following processes is catalyzed by reverse transcriptase in retroviruses?

Accepted Answer

Synthesis of DNA from an RNA template

Question 19

A researcher is studying the fidelity of DNA replication. Which activity of DNA polymerase is most directly responsible for proofreading and excising mismatched nucleotides?

Accepted Answer

3'-exonuclease activity

DNA Replication: Mechanisms and Molecular Components

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