The diameter of the DNA double helix is:
A10 nanometres
B1 nanometre
C2 nanometres
D5 nanometres
Answer & Solution
Correct answer: C. 2 nanometres
1. A purine always pairs with a pyrimidine, so every rung is the same width.
2. That is why the helix does not bulge or pinch along its length.
3. The diameter of the DNA double helix is 2 nanometres, and it is uniform throughout.
4. Ten nanometres is the width of a nucleosome bead, not of bare DNA.
_Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 14 'DNA Structure and Function', sections 14.1-14.6_
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