Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 2

In the Meselson-Stahl experiment, what result after two rounds of replication in 14N medium would support the semiconservative model?

Accepted Answer

One band of intermediate density and one band of light density.

Question 3

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

Accepted Answer

It adds DNA nucleotides to the 3' end of a growing DNA strand.

Question 4

Which enzyme is responsible for relieving the strain caused by unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 5

Why are Okazaki fragments formed during DNA replication?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the 5' to 3' direction, requiring discontinuous synthesis on the lagging strand.

Question 6

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

Accepted Answer

They stabilize unwound DNA strands and prevent them from re-pairing.

Question 7

Which of the following best explains why DNA polymerase requires a primer to begin synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' hydroxyl group.

Question 8

During nucleotide addition, which chemical reaction provides the energy for the formation of the new phosphodiester bond?

Accepted Answer

Hydrolysis of the pyrophosphate group ($$PP_i) $$released from the incoming nucleotide triphosphate.

Question 9

A mutation in which enzyme would most likely result in the inability to join Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 10

Which of the following statements about telomeres is correct?

Accepted Answer

Telomeres are repetitive, noncoding sequences that protect the ends of eukaryotic chromosomes from erosion.

Question 11

What is the function of the enzyme telomerase in eukaryotic germ cells?

Accepted Answer

It extends the length of telomeres, compensating for shortening during DNA replication.

Question 12

A patient with xeroderma pigmentosum is highly sensitive to sunlight. This is most likely due to a defect in which DNA repair process?

Accepted Answer

Nucleotide excision repair

Question 13

Which of the following best explains the evolutionary significance of rare, uncorrected mutations in DNA?

Accepted Answer

They are the source of genetic variation on which natural selection acts.

Question 14

Which of the following is a direct consequence of the antiparallel structure of DNA for the process of replication?

Accepted Answer

One strand is synthesized continuously, while the other is synthesized in fragments.

Question 15

If a mutation prevented the function of primase, what would be the most immediate effect on DNA replication?

Accepted Answer

DNA polymerase would be unable to begin synthesizing new DNA strands.

Question 16

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

Accepted Answer

It joins the sugar-phosphate backbones of Okazaki fragments to form a continuous DNA strand.

Question 17

A defect in which of the following enzymes would most likely increase the mutation rate in a cell due to failure to correct mismatched base pairs during DNA replication?

Accepted Answer

DNA polymerase

Question 18

Which of the following is a real-world consequence of a failure in DNA repair mechanisms?

Accepted Answer

Increased risk of cancer due to accumulation of mutations.

Question 19

During DNA replication, which direction does DNA polymerase synthesize the new strand?

Accepted Answer

5' to 3' direction

Question 20

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

Accepted Answer

To allow rapid and efficient replication of large DNA molecules.

DNA Replication and Repair: Mechanisms and Molecular Players

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