Question

What is the pitch (vertical rise per complete turn) of the DNA double helix?

Options

• 10 Å

• 2 nm

• 34 Å

• 3.4 Å

Answer 1

The pitch of the DNA double helix is 34 ångströms (Å) per complete turn. The pitch represents the vertical distance along the helix axis for one complete 360° rotation. Combined with the 3.4 Å spacing between adjacent base pairs, the pitch confirms the 10 base pairs per turn measurement. The pitch is a critical structural parameter in the Watson-Crick model.