Question

The distance between adjacent nucleotides in DNA is:

• A. 0.15 nm
• B. 0.34 nm
• C. 3.0 Å
• D. 3.1 Å

Hint:

Remember that the rise per base pair in the DNA double helix (B-DNA) is 0.34 nm (3.4 Å), and one full turn of the helix contains about 10.5 base pairs.

Answer 1

The Correct Option is B

Step 1: Understanding the structure of DNA.
DNA exists in the form of a double helix where nucleotides are stacked one above the other in a very specific manner. Each nucleotide consists of a base, sugar, and phosphate group. The spatial arrangement gives a uniform helical structure.
Step 2: Distance between nucleotides.
The correct distance between two successive nucleotides along the helix axis is 0.34 nanometers (nm), which is equivalent to 3.4 Å. This measurement has been confirmed by X-ray crystallography studies (notably by Rosalind Franklin).
Step 3: Eliminating incorrect options.
- Option (1) 0.15 nm: Too short to represent the actual stacking distance.
- Option (3) 3.0 Å: Slightly less than the accurate known distance.
- Option (4) 3.1 Å: Also incorrect, as the true value is closer to 3.4 Å.
Thus, the most precise answer is 0.34 nm.
Final Answer:
\[ \boxed{0.34 \, \text{nm}} \]