Ques. 1AIPMT 2000
Length of one loop of B-DNA:
- 20 nm.
- 10 nm.
- 3.4 nm.
- 0.34 nm.
Answer
(3) 3.4 nm.
Solution
As per NCERT, the pitch of the B-DNA helix is 3.4 nm (a nm is 10-9 m) and there are roughly 10 bp in each turn.
∴ Length of one turn (loop) = 10 0.34 nm = 3.4 nm (distance between two adjacent base pairs = 0.34 nm).
Answer: (3)