Question 1

Which of the following experiments provided the most direct evidence that DNA, and not protein, is the hereditary material in bacteriophages?

Accepted Answer

Hershey and Chase’s radioactive labeling experiment using $$^{32}P$$ and $$^{35}S$$

Question 2

Which property of DNA allows it to serve as a template for its own replication?

Accepted Answer

Its complementary and antiparallel strand structure

Question 3

In the Meselson-Stahl experiment, after two rounds of replication in $$^{14}N$$ medium, what proportion of DNA molecules are expected to be 'light' ($$^{14}N$$/^{14}$$N) $$and 'hybrid' ($$^{15}N$$/^{14}$$N) if $$DNA replication is semiconservative?

Accepted Answer

Half are light and half are hybrid

Question 4

Which enzyme is responsible for relieving torsional stress and supercoiling ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 5

Which of the following best describes the difference between the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments called Okazaki fragments.

Question 6

Which DNA form is most commonly found in living cells and is characterized by a right-handed helix with a diameter of 20 Å?

Accepted Answer

B-form DNA

Question 7

A mutation in the gene encoding DNA polymerase I in E. coli results in the inability to remove RNA primers. What is the most likely consequence?

Accepted Answer

Okazaki fragments will remain unjoined due to the presence of RNA primers.

Question 8

Which of the following statements about telomerase is correct?

Accepted Answer

Telomerase is a ribonucleoprotein that extends telomeres using an RNA template.

Question 9

Which of the following best explains why DNA polymerase has a low error rate during replication?

Accepted Answer

It has 3' to 5' exonuclease proofreading activity.

Question 10

Which of the following sequences is most likely to be found at the origin of replication in E. coli, based on consensus sequence analysis?

Accepted Answer

TTATCCACA

Question 11

A scientist is studying a new archaeal species and finds that its genome contains four distinct origin recognition bases (ORBs). What does this suggest about its DNA replication?

Accepted Answer

Replication initiates at multiple origins.

Question 12

Which of the following is a direct result of the antiparallel nature of DNA strands?

Accepted Answer

Hydrogen bonds form between complementary bases.

Question 13

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

Accepted Answer

Primase

Question 14

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

Accepted Answer

It joins Okazaki fragments by forming phosphodiester bonds.

Question 15

A patient’s cancer cells are found to have abnormally high telomerase activity. What is the most likely consequence of this observation?

Accepted Answer

The cancer cells will maintain telomere length, contributing to unlimited cell division.

Question 16

Which of the following is a pyrimidine base found in DNA?

Accepted Answer

Thymine

Question 17

Which of the following statements about the major and minor grooves of DNA is correct?

Accepted Answer

They are formed by the base-pair stacking and are sites for protein binding.

Question 18

Which of the following best explains why the 13-mer region of oriC in E. coli is rich in A-T base pairs?

Accepted Answer

A-T base pairs are easier to separate due to having only two hydrogen bonds.

Question 19

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 newly synthesized strand.

DNA Structure and Replication: Molecular Basis and Mechanisms

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