How Many Bases are Necessary to Complete One Complete Twist

Question

How many bases are necessary to complete one complete twist (360 degrees)of a DNA double helix?
A) 5
B) 10
C) 100
D) 1000

Accepted Answer

One complete twist (360 degrees) of a DNA double helix requires 10 nucleotide base pairs. Each turn of the helix involves 3.4 nanometers of distance along the axis of the helix, and an average of 0.34 nm of vertical rise. This means that each turn requires 10 base pairs to cover the complete twist. Therefore, the correct answer is B) 10.