The rise and pitch of B-DNA are 0.33 nm and 3.40 nm,respectively.About how many helical turns are there in a fragment 1000 nm in length?

Question

Quizplus · Accepted Answer

The rise per helical turn for B-DNA is 0.34 nm, but in this case, we are given a rise of 0.33 nm which suggests that there is some base-pair distortion. Therefore, we can round off to the nearest permissible rise of 0.34 nm.
Total number of helical turns = Length of fragment / Pitch per turn
= 1000 nm / 3.4 nm/turn ≈ 294 turns.

The Rise and Pitch of B-DNA Are 0