Question 1

Which hypothesis for DNA replication was supported by the results of the Meselson and Stahl experiment using $$^{15}N-$$labeled E. coli?

Accepted Answer

Semiconservative replication

Question 2

During DNA replication, which enzyme is responsible for unwinding the double helix at the origin of replication?

Accepted Answer

DNA helicase

Question 3

What is the primary function of single-stranded binding proteins (SSBPs) during DNA replication?

Accepted Answer

To stabilize the unwound DNA strands and prevent them from reannealing

Question 4

Which DNA polymerase in prokaryotes is mainly responsible for the 5' to 3' polymerization during DNA replication?

Accepted Answer

DNA polymerase III

Question 5

In the process of lagging strand synthesis, which enzyme removes the RNA primer and fills in the gap with DNA nucleotides?

Accepted Answer

DNA polymerase I

Question 6

What is the role of DNA gyrase during DNA replication in prokaryotes?

Accepted Answer

To relieve supercoiling ahead of the replication fork

Question 7

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

Accepted Answer

5' to 3' direction

Question 8

A mutation disables the 3' to 5' exonuclease activity of DNA polymerase III. What is the most likely consequence?

Accepted Answer

The error rate during DNA replication will increase

Question 9

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

Accepted Answer

Eukaryotic chromosomes are linear and have multiple origins of replication

Question 10

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

Accepted Answer

Shortening of chromosome ends; solved by telomerase

Question 11

Which enzyme synthesizes the short RNA primer required for DNA polymerase to initiate synthesis?

Accepted Answer

Primase

Question 12

In rolling circle replication, which of the following is TRUE?

Accepted Answer

A single-stranded nick initiates replication and the leading strand is synthesized continuously

Question 13

Which of the following is a function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments by forming phosphodiester bonds

Question 14

A patient with Hutchinson-Gilford syndrome shows premature aging. Which molecular process is most likely defective?

Accepted Answer

Telomerase activity and telomere maintenance

Question 15

Which equation correctly represents the semiconservative model of DNA replication after one round, assuming the original DNA is labeled with $$^{15}N$$ and new nucleotides are $$^{14}N$$?

Accepted Answer

$$100\%$$ $$^{15}N$$/^{14}$$N$$ hybrid DNA

Question 16

Which of the following is NOT a strict requirement for DNA replication?

Accepted Answer

Synthesis of Okazaki fragments on the leading strand

Question 17

During homologous recombination, which structure is formed as a result of strand invasion and exchange between homologous chromosomes?

Accepted Answer

Holliday junction

Question 18

Which process is responsible for correcting errors that escape DNA polymerase proofreading during replication?

Accepted Answer

Mismatch repair

Question 19

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

Accepted Answer

DNA polymerase $$\varepsilon$$

Question 20

A scientist observes that a cell line maintains telomere length indefinitely. What is the most likely explanation?

Accepted Answer

The cells have active telomerase enzyme

Lecture 9 (ch 11)

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