According to the B-DNA structural model described by Watson and Crick, what are the pitch of the helix and the distance between two successive base pairs?
Answer and explanation
Correct answer: D. Pitch is 3.4 nm and distance between base pairs is 0.34 nm
- Step 1: In the standard physiological right-handed B-DNA double helix, each full turn comprises approximately base pairs.
- Step 2: The vertical pitch (length of one complete helical turn) measures ().
- Step 3: Dividing the pitch by the number of base pairs per turn gives the axial rise per base pair: ().
Answer
Pitch is () and distance between base pairs is ().
Why not the others: is the outer helical diameter of the B-DNA cylinder; corresponds to A-DNA pitch; assumes 20 base pairs per helical turn.
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