Question

Diameter of DNA double helix is _______.

• A. 34$A^{\circ }$
• B. 20$A^{\circ }$
• C. 3.4$A^{\circ }$
• D. 340$A^{\circ }$

Answer 1

Answer: (B)

20$A^{\circ }$

The diameter of the DNA helix is 2nm or 20$A^{\circ }$ and the vertical rise per base pair is 0.34nm. A DNA molecule is composed of two unbranched polynucleotide chains (strands) that wind about each other into a structure called a double helix.

Hence the correct answer is (B)