Question

Distance between two successive base pairs in DNA is

• A. $0.34nm$
• B. $0.34\mathring{A}$
• C. $3.4nm$
• D. $34\mathring{A}$

Answer 1

The correct option is A $0.34nm$

The diameter of the B-DNA is 20 Angstroms, and the distance between base pairs is 3.4 Angstroms or 0.34 nm. The base pairing of opposite strands is stereochemically selective, adenine always pairing with thymine, and guanine with cytosine. Two and three hydrogen bonds are formed in A-T and G-C base pairs, respectively. In Z-DNA which is thinner than B-DNA, average distance per base pair along the DNA axis is 0.38 nm, and in A-DNA which is thicker it is 0.23 nm. So, the correct answer is '0.34nm'.