Question 1

Which experimental result from the Meselson-Stahl experiment provided the strongest evidence against the dispersive model of DNA replication after two generations in 14N medium?

Accepted Answer

The presence of both light and hybrid DNA bands after two generations

Question 2

What is the primary function of DNA polymerase III in E. coli during DNA replication?

Accepted Answer

Synthesis of the leading and lagging DNA strands

Question 3

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

Accepted Answer

DNA is synthesized in the 5' to 3' direction

Question 4

Why do eukaryotic chromosomes require multiple origins of replication?

Accepted Answer

Because eukaryotic chromosomes are much larger and require simultaneous replication at multiple sites

Question 5

Which enzyme is responsible for relieving the supercoiling tension generated ahead of the replication fork during DNA replication?

Accepted Answer

DNA gyrase (a type of topoisomerase)

Question 6

What is the role of single-stranded binding proteins during DNA replication?

Accepted Answer

They stabilize unwound DNA strands to prevent re-annealing

Question 7

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand

Question 8

A mutation in the gene encoding DNA ligase would most directly affect which step of DNA replication?

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 9

Which of the following best explains 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

What is the function of telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' ends of chromosomes using an RNA template

Question 11

Which of the following sequences is most likely to be found at the end of a human chromosome?

Accepted Answer

$$5'	ext{-}TTAGGG-3'$$

Question 12

Which of the following is NOT a function of DNA polymerase I in E. coli?

Accepted Answer

Synthesizing the majority of the leading strand

Question 13

A patient’s cells are found to have abnormally short telomeres and reduced cell division capacity. Which enzyme is most likely deficient?

Accepted Answer

Telomerase

Question 14

Which of the following best describes the role of primase during DNA replication?

Accepted Answer

It synthesizes a short RNA primer to provide a free 3'-OH group for DNA polymerase

Question 15

Which of the following equations correctly represents the addition of a nucleotide during DNA synthesis?

Accepted Answer

$$(dNMP)_n + dNTP \xrightarrow{DNA\ polymerase} (dNMP)_{n+1} + PP_i$$

Question 16

Which of the following is a direct consequence of the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental and one new strand

Question 17

Which enzyme is responsible for synthesizing the RNA primer required for DNA polymerase to initiate DNA synthesis?

Accepted Answer

Primase

Question 18

In the context of cancer biology, why is telomerase activity often upregulated in cancer cells?

Accepted Answer

To maintain telomere length and allow unlimited cell division

Question 19

Which of the following best explains why DNA replication is bidirectional in both prokaryotes and eukaryotes?

Accepted Answer

Replication forks move away from the origin in both directions, allowing simultaneous synthesis of DNA on both sides

DNA Replication: Mechanisms, Enzymes, and Chromosome End Replication

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