Question 1

Which enzyme is responsible for catalyzing the separation of DNA strands to open the double helix during DNA replication?

Accepted Answer

Helicase

Question 2

During DNA replication, which protein binds to and stabilizes single-stranded DNA to prevent it from re-annealing or being degraded before lagging strand synthesis?

Accepted Answer

Single-strand binding proteins (SSBs)

Question 3

Which enzyme synthesizes short RNA primers needed to initiate DNA synthesis on both the leading and lagging strands?

Accepted Answer

Primase

Question 4

A patient is treated with a drug that inhibits the enzyme responsible for relieving the twisting tension ahead of the replication fork. Which enzyme is being targeted?

Accepted Answer

Topoisomerase

Question 5

Which enzyme holds the DNA template in place during the extension of a new DNA strand, ensuring high processivity?

Accepted Answer

Sliding clamp

Question 6

Which enzyme is responsible for extending the leading strand of DNA during replication by adding nucleotides in the 5' to 3' direction?

Accepted Answer

DNA polymerase III

Question 7

After the RNA primer is removed from the lagging strand, which enzyme fills in the resulting gap with DNA nucleotides?

Accepted Answer

DNA polymerase I

Question 8

What are the short DNA fragments called that are synthesized discontinuously on the lagging strand during DNA replication?

Accepted Answer

Okazaki fragments

Question 9

Which enzyme catalyzes the joining of Okazaki fragments to form a continuous DNA strand?

Accepted Answer

Ligase

Question 10

Which model of DNA replication is supported by experimental evidence such as the Meselson-Stahl experiment?

Accepted Answer

Semiconservative model

Question 11

Where would you expect to find telomeres in a eukaryotic chromosome?

Accepted Answer

At the ends of linear chromosomes

Question 12

Which enzyme can extend the ends of chromosomes to prevent them from shortening after each round of DNA replication?

Accepted Answer

Telomerase

Question 13

Which enzyme initiates the DNA proofreading process by checking and correcting mismatched nucleotides during DNA synthesis?

Accepted Answer

DNA polymerase III

Question 14

If DNA polymerase fails to correct an error during replication, which repair mechanism is most likely to fix the mistake?

Accepted Answer

Mismatch repair

Question 15

Exposure to UV light can cause which specific type of mutation in DNA?

Accepted Answer

Formation of thymine dimers

Question 16

Which enzyme system is primarily responsible for repairing thymine dimers caused by UV radiation in DNA?

Accepted Answer

Nucleotide excision repair enzymes

Question 17

A young patient develops skin cancer at an early age due to an inability to repair UV-induced DNA damage. Which genetic disorder is most likely responsible?

Accepted Answer

Xeroderma pigmentosum

Question 18

A scientist is studying a eukaryotic cell line that lacks functional telomerase. What is the most likely long-term consequence for these cells after multiple rounds of cell division?

Accepted Answer

Progressive shortening of chromosomes leading to cell senescence

Question 19

If a mutation disables the sliding clamp protein during DNA replication, which of the following outcomes is most likely?

Accepted Answer

DNA polymerase will frequently dissociate from the template, reducing replication efficiency

Question 20

A researcher exposes bacterial cells to UV light and then observes that the cells are unable to repair thymine dimers. Which DNA repair pathway is most likely defective in these cells?

Accepted Answer

Nucleotide excision repair

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