Question 1

Which of the following best describes the main conclusion from Fredrick Griffith’s experiment with Streptococcus pneumoniae?

Accepted Answer

A hereditary factor from heat-killed S strain can transform live R strain into a virulent form.

Question 2

In Avery’s experiments, which enzyme treatment prevented transformation of R cells into S cells, and what did this indicate?

Accepted Answer

DNase; DNA is the genetic material.

Question 3

Which radioactive isotope did Hershey and Chase use to label DNA in their experiments, and what was the significance of their findings?

Accepted Answer

$$^{32}\mathrm{P}$$; it showed that DNA is the hereditary material.

Question 4

What did Erwin Chargaff’s experiments reveal about the composition of DNA?

Accepted Answer

The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Question 5

Which scientist’s X-ray crystallography images were critical in the discovery of the DNA double helix structure?

Accepted Answer

Rosalind Franklin

Question 6

If a DNA sample contains 30% adenine, what percentage of guanine would you expect to find according to Chargaff’s rules?

Accepted Answer

20%

Question 7

Which of the following best explains why the S strain of Streptococcus pneumoniae is virulent?

Accepted Answer

It has a polysaccharide capsule that protects it from the host’s immune system.

Question 8

In the Hershey-Chase experiment, what was the purpose of using a blender after infection of E. coli with bacteriophages?

Accepted Answer

To remove the viral coats from the surface of the bacterial cells.

Question 9

Which of the following is a direct result of transformation as observed by Griffith?

Accepted Answer

Live R cells become capable of causing disease after exposure to heat-killed S cells.

Question 10

Which of the following statements about the structure of DNA is correct based on Watson and Crick’s model?

Accepted Answer

DNA is a double helix with complementary base pairing between purines and pyrimidines.

Question 11

A scientist destroys all RNA in a sample of heat-killed S cells and mixes it with live R cells. What is the expected outcome based on Avery’s experiments?

Accepted Answer

R cells will be transformed into S cells.

Question 12

Which experimental result would refute the conclusion that DNA is the hereditary material?

Accepted Answer

If $$^{32}\mathrm{P}$$ was not found inside the bacterial cells after phage infection.

Question 13

Which of the following best describes the relationship between purines and pyrimidines in DNA?

Accepted Answer

Purines pair with pyrimidines, maintaining a constant width of the DNA helix.

Question 14

A patient is infected with a strain of bacteria that lacks a polysaccharide capsule. Based on Griffith’s findings, what is the likely outcome?

Accepted Answer

The bacteria will not cause disease unless transformed by genetic material from a virulent strain.

Question 15

Which of the following is a real-world application of the concept of transformation discovered by Griffith?

Accepted Answer

Genetically engineering bacteria to produce human insulin.

Question 16

If a DNA molecule contains 24% cytosine, what percentage of thymine would you expect to find?

Accepted Answer

26%

Question 17

Which of the following best explains why protein was initially considered a candidate for the genetic material?

Accepted Answer

Proteins are composed of 20 different amino acids, allowing for greater complexity.

Question 18

What is the significance of the equal ratios of A to T and G to C in DNA?

Accepted Answer

It supports the idea of complementary base pairing.

Question 19

Which of the following experimental approaches would best test whether a molecule is the genetic material?

Accepted Answer

Label the molecule with a radioactive isotope and track its entry into cells during infection.

Molecular Biology of the Gene: Key Experiments and Discoveries

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