Question 1

According to Chargaff's rules, which of the following equations correctly represents the base pairing in double-stranded DNA?

Accepted Answer

$$[A] = [T]$$ and $$[G] = [C]$$

Question 2

Watson and Crick used X-ray crystallography images to deduce the structure of DNA. Which scientist's work provided the critical image that led to their discovery?

Accepted Answer

Rosalind Franklin

Question 3

Which feature of the DNA double helix allows proteins to recognize specific base sequences without unwinding the helix?

Accepted Answer

The major and minor grooves

Question 4

If a DNA molecule contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

20%

Question 5

Which of the following best describes the conformation of DNA under physiological conditions?

Accepted Answer

B-form

Question 6

What is the significance of the antiparallel arrangement of the two DNA strands?

Accepted Answer

It enables the formation of hydrogen bonds between complementary bases.

Question 7

Which chemical bond is responsible for linking nucleotides together in a single strand of DNA?

Accepted Answer

Phosphodiester bond

Question 8

A mutation causes a cytosine to be replaced by a thymine in one strand of DNA. Which of the following is a likely consequence?

Accepted Answer

The hydrogen bonding pattern will be disrupted, possibly causing a bulge in the helix.

Question 9

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

Accepted Answer

Nucleotides in DNA can freely rotate around the glycosidic bond, allowing for Z-form DNA under physiological conditions.

Question 10

Which of the following best explains why DNA is more stable than RNA under physiological conditions?

Accepted Answer

DNA contains deoxyribose, which lacks a 2'-hydroxyl group, making it less susceptible to hydrolysis.

Question 11

Which of the following is a direct consequence of the major and minor grooves in DNA?

Accepted Answer

They provide access for proteins to interact with specific base pairs.

Question 12

A scientist isolates a DNA sample and finds that it has 24% guanine. What is the expected percentage of thymine in this sample?

Accepted Answer

26%

Question 13

Which of the following best describes the hydrogen bonding between base pairs in DNA?

Accepted Answer

Adenine forms two hydrogen bonds with thymine, and guanine forms three hydrogen bonds with cytosine.

Question 14

Which of the following is a correct representation of a nucleotide found in DNA?

Accepted Answer

A phosphate group, a deoxyribose sugar, and a nitrogenous base

Question 15

Which of the following best explains why the DNA double helix has a uniform diameter?

Accepted Answer

Purines always pair with pyrimidines, maintaining a constant width.

Nucleic Acids: Structure and Properties of DNA

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