Question

In a DNA molecule distance between two bases is

• A. $2nm/20\stackrel{o}{A}$
• B. $0.2nm/2\stackrel{o}{A}$
• C. $3.4nm/34\stackrel{o}{A}$
• D. $0.34nm/3.4\stackrel{o}{A}$

Answer 1

The correct option is D $0.34nm/3.4\stackrel{o}{A}$

According to Watson and Crick model of DNA, the DNA molecule is made up of two helical DNA chains that are wound around the same axis. The hydrophilic backbones of alternating sugar and phosphate groups are present on the outside of the double helix facing the surrounding water. The nitrogenous bases, purine and pyrimidine are stacked inside the double helix. Each nucleotide base of one strand is paired in the same plane with a base of the other strand. Since, one complete turn of the double helix is 3.4 nm long and each of which has 10 base pairs, the distance between two consecutive base pairs should be 3.4/10 = 0.34 nm.

Thus, the correct answer is option D.