Question

The length of one turn of the helix in B-form DNA is approximately

• A. 0.34 nm
• B. 20 nm
• C. 2nm
• D. 3.4 nm

Answer 1

Answer: (D)

B-form of DNA shows right-handed coiling which contains $10$ base pairs in each turn. On complete turn, DNA occupies $34$ A distance.
So in nm, it will $3.4nm$ because or.
$1nm=10^{-9}m$
$1\mathring{A}=10^{10}m$
So $34\mathring{A}=34x10^{10}m$
$=3.4nm$