Question 1

Which of the following best describes the semiconservative model of DNA replication as demonstrated by the Meselson-Stahl experiment?

Accepted Answer

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

Question 2

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

Accepted Answer

Primase

Question 3

What is the main function of DNA polymerase III in E. coli?

Accepted Answer

Synthesizing the leading and lagging strands during DNA replication

Question 4

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

Accepted Answer

DNA polymerase adds nucleotides to the 3' end, so synthesis proceeds in the 5' to 3' direction.

Question 5

Which of the following is a key reason why DNA replication is highly accurate?

Accepted Answer

DNA polymerase has a 3' to 5' exonuclease activity that proofreads and removes misincorporated nucleotides.

Question 6

In the Meselson-Stahl experiment, after two generations in ¹⁴N medium, what fraction of DNA molecules are expected to be 'light' and what fraction 'hybrid'?

Accepted Answer

$$\frac{1}{2}$$ light, $$\frac{1}{2}$$ hybrid

Question 7

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

Accepted Answer

A free 5' phosphate group to initiate synthesis

Question 8

What is the role of DNA ligase during DNA replication?

Accepted Answer

It covalently attaches adjacent Okazaki fragments on the lagging strand.

Question 9

Why is the replication of eukaryotic chromosomes more complex than that of prokaryotic chromosomes?

Accepted Answer

Eukaryotic chromosomes are linear, have multiple origins of replication, and are tightly packaged with nucleosomes.

Question 10

What is the function of telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' overhang at chromosome ends, allowing a primer to be placed for complete replication.

Question 11

A mutation in DNA polymerase III eliminates its 3' to 5' exonuclease activity. What is the most likely consequence?

Accepted Answer

The mutation rate during DNA replication will increase.

Question 12

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is synthesized discontinuously.

Question 13

Which of the following is a correct description of a nucleotide in DNA?

Accepted Answer

A nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base.

Question 14

Which of the following is a function of the DnaA protein in E. coli DNA replication?

Accepted Answer

It binds to DnaA boxes within the origin to initiate DNA replication.

Question 15

Which of the following statements about telomeres is correct?

Accepted Answer

Telomeres are repetitive DNA sequences found at the ends of linear chromosomes.

Question 16

In eukaryotic DNA replication, which polymerase is primarily responsible for synthesizing the leading strand?

Accepted Answer

DNA polymerase $$\varepsilon$$

Question 17

A bacterial cell is exposed to a chemical that inhibits DNA gyrase. What is the most likely effect on DNA replication?

Accepted Answer

Replication will stall due to positive supercoiling ahead of the replication fork.

Question 18

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

Accepted Answer

Their large size and linear structure require multiple starting points to ensure timely replication.

Question 19

Which of the following is a real-world consequence of telomerase activity in human cells?

Accepted Answer

Telomerase activity is high in stem cells and most cancer cells, contributing to their ability to divide indefinitely.

DNA Replication: Mechanisms, Enzymes, and Regulation

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