Question 1

Which experiment provided the first direct evidence that DNA, and not protein, is the hereditary material responsible for bacterial transformation?

Accepted Answer

The Avery, MacLeod, and McCarty experiment using enzymatic digestion of macromolecules

Question 2

Which of the following is NOT a characteristic required of hereditary material?

Accepted Answer

It must be composed only of proteins.

Question 3

In the Hershey-Chase experiment, why was $$^{32}P$$ used to label DNA and $$^{35}S$$ used to label protein?

Accepted Answer

$$^{32}P is $$found in DNA but not in protein, and $$^{35}S is $$found in protein but not in DNA.

Question 4

Which of the following best describes the chemical bond that links nucleotides together in a single DNA strand?

Accepted Answer

Phosphodiester bond between the 3' hydroxyl and 5' phosphate

Question 5

A DNA molecule is analyzed and found to contain 30% adenine. According to Chargaff’s rule, what percentage of guanine would you expect to find?

Accepted Answer

20%

Question 6

Which feature of the DNA double helix is essential for the formation of stable hydrogen bonds between complementary bases?

Accepted Answer

The antiparallel orientation of the two strands

Question 7

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The bases are paired in the center of the helix via hydrogen bonds.

Question 8

A mutation changes a cytosine to a thymine in one strand of DNA. What is the most likely effect on base pairing?

Accepted Answer

The thymine will pair with adenine, forming two hydrogen bonds.

Question 9

Which groove in the DNA double helix is wider and more accessible to DNA-binding proteins?

Accepted Answer

The major groove, approximately 12 Å wide

Question 10

Which of the following best explains why DNA is considered a complex informational molecule despite its structural simplicity?

Accepted Answer

The sequence of its four nucleotides encodes genetic information.

Question 11

A scientist isolates a nucleic acid from a virus and finds that it contains ribose sugar and uracil. What type of molecule is this?

Accepted Answer

RNA

Question 12

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

Accepted Answer

Adenine

Question 13

What is the distance between adjacent base pairs in the DNA double helix?

Accepted Answer

$$3.4\ 	ext{Å}$$

Question 14

Which enzyme catalyzes the formation of phosphodiester bonds during DNA strand elongation?

Accepted Answer

DNA polymerase

Question 15

In Griffith’s experiment, what was the outcome when mice were injected with a mixture of heat-killed SIII bacteria and live RII bacteria?

Accepted Answer

The mice died and live SIII bacteria were recovered.

Question 16

Which of the following best describes the antiparallel nature of DNA strands?

Accepted Answer

One strand runs 5' to 3', the other runs 3' to 5'.

Question 17

A DNA sample is found to have 28% thymine. What is the expected percentage of cytosine in this sample?

Accepted Answer

22%

Question 18

Which scientist’s x-ray diffraction data was critical in determining the double helical structure of DNA?

Accepted Answer

Rosalind Franklin

Question 19

Which of the following is a property of deoxyribose that distinguishes it from ribose?

Accepted Answer

Deoxyribose lacks an OH group at the 2' carbon.

Question 20

Which of the following best explains why the DNA double helix has a uniform diameter of $$20\ 	ext{Å}$$?

Accepted Answer

Base pairing always occurs between a purine and a pyrimidine.

DNA Structure: The Molecular Basis of Heredity

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