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 use of radioactive isotopes to label DNA and protein in phages

Question 2

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

Accepted Answer

The antiparallel and complementary nature of its two strands

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' ($$^{14}N$$/^{15}$$N) if $$DNA replication is semiconservative?

Accepted Answer

Half are light and half are hybrid

Question 4

Which enzyme is responsible for relieving torsional stress and preventing supercoiling 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-DNA

Question 7

What is the function of DNA polymerase I during DNA replication in E. coli?

Accepted Answer

It removes RNA primers and replaces them with DNA nucleotides.

Question 8

Which of the following statements about telomerase is TRUE?

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 high fidelity during DNA replication?

Accepted Answer

It has 3' to 5' exonuclease activity for proofreading.

Question 10

A mutation in the gene encoding single-stranded binding protein (SSB) would most likely result in which of the following problems during DNA replication?

Accepted Answer

Reannealing of separated DNA strands, preventing replication

Question 11

Which of the following sequences is most likely to be found at the origin of replication in E. coli (oriC)?

Accepted Answer

A region containing multiple 13-mer and 9-mer A-T rich consensus sequences

Question 12

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

Accepted Answer

Complementary base pairing occurs, allowing for accurate replication.

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 role of hydrogen bonds in the DNA double helix?

Accepted Answer

They stabilize the pairing between complementary bases on opposite strands.

Question 15

A researcher isolates a DNA molecule with a left-handed helix and a diameter of 18 Å. Which form of DNA is this most likely to be?

Accepted Answer

Z-DNA

Question 16

Which of the following is a real-world implication of telomerase activity in human cells?

Accepted Answer

Activation of telomerase in somatic cells could increase cell longevity but may also increase cancer risk.

Question 17

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are joined together by DNA ligase after RNA primers are replaced with DNA.

Question 18

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

Accepted Answer

A-T base pairs have only two hydrogen bonds, making the region easier to unwind during replication initiation.

Question 19

Which of the following is NOT a characteristic required of hereditary material, as identified before DNA was known to be the hereditary molecule?

Accepted Answer

It must be able to catalyze metabolic reactions.

DNA Structure and Replication: Foundations of Heredity

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