Question 1

Which of the following best describes the mode of DNA replication demonstrated by the Meselson and Stahl experiment?

Accepted Answer

Semiconservative replication, where each daughter DNA molecule contains one parental and one newly synthesized strand.

Question 2

During the initiation of DNA replication in prokaryotes, which enzyme is responsible for relieving torsional strain ahead of the replication fork?

Accepted Answer

DNA gyrase (a type of topoisomerase)

Question 3

What is the primary function of single-strand binding proteins during DNA replication?

Accepted Answer

They prevent the re-annealing of single-stranded DNA, keeping the strands separated for replication.

Question 4

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

Accepted Answer

DNA polymerase synthesizes DNA in the 5' to 3' direction.

Question 5

In eukaryotic cells, what problem arises at the ends of linear chromosomes during DNA replication, and how is it resolved?

Accepted Answer

The ends cannot be fully replicated, leading to telomere shortening, which is counteracted by the enzyme telomerase.

Question 6

Which enzyme is responsible for synthesizing short RNA primers during DNA replication?

Accepted Answer

Primase

Question 7

What is the role of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments on the lagging strand by forming phosphodiester bonds.

Question 8

A mutation in the gene encoding the clamp loader protein would most likely result in which of the following?

Accepted Answer

Inability of DNA polymerase to remain attached to the DNA template, leading to inefficient DNA synthesis.

Question 9

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so synthesis occurs in short fragments away from the replication fork.

Question 10

Which of the following equations correctly represents the base-pairing rule during DNA replication?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 11

A patient’s cells are found to have a high rate of mutations during DNA replication. Which enzyme is most likely defective?

Accepted Answer

DNA polymerase (proofreading function)

Question 12

In the Meselson and Stahl experiment, after one round of replication in $$^{14}N$$ medium, what was the density of the DNA observed?

Accepted Answer

All DNA was of intermediate density (hybrid)

Question 13

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

Accepted Answer

Eukaryotes have multiple origins of replication, while prokaryotes typically have a single origin.

Question 14

Which enzyme removes RNA primers from the lagging strand during DNA replication?

Accepted Answer

RNAse H

Question 15

A scientist observes that after several rounds of cell division, the chromosomes in a cell line become progressively shorter. What is the most likely explanation?

Accepted Answer

The cells lack functional telomerase, leading to telomere shortening.

Question 16

Which of the following best describes the function of telomerase?

Accepted Answer

It extends the ends of linear chromosomes using an RNA template.

Question 17

Which of the following is the correct sequence of events during the initiation of DNA replication?

Accepted Answer

Binding of initiator proteins, unwinding by helicase, stabilization by single-strand binding proteins

Question 18

Which of the following equations represents the error rate of DNA polymerase after proofreading?

Accepted Answer

$$1$$ error per $$10^7$$ - $$10^8$$ nucleotides$

Question 19

Which of the following is a real-life consequence of defective DNA replication termination in bacteria?

Accepted Answer

Failure to separate daughter DNA molecules, leading to cell division defects.

Question 20

Which enzyme is responsible for decatenating interlocked daughter DNA molecules after replication?

Accepted Answer

Topoisomerase

DNA Replication: Mechanisms, Proteins, and Differences in Prokaryotes and Eukaryotes

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