DNA Structure · Botany

The width of a standard B-DNA double helix is approximately:

  1. 2.0 nm
  2. 3.4 nm
  3. 0.34 nm
  4. 20 nm
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Correct answer: 2.0 nm

The diameter of the B-DNA double helix is constant at 2 nanometers (20 Å). This uniform width is maintained because a purine always pairs with a pyrimidine.

Difficulty: Medium Question 7 of 20

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