LIFE SCIENCE

Detailed explanation-1: -The variation of energy with the twist of the base pairs about the helix axis shows the straight DNA free in solution is most stable with about 10 1/2 base pairs per turn rather than 10 as observed in the solid state, whereas superhelical DNA in chromatin is most stable with about 10 base pairs per turn.

Detailed explanation-2: -The bases are nearly perpendicular to the helix axis, and adjacent bases are separated by 3.4 . The helical structure repeats every 34, so there are 10 bases (= 34 per repeat/3.4 per base) per turn of helix. There is a rotation of 36 degrees per base (360 degrees per full turn/10 bases per turn).

Detailed explanation-3: -In B-DNA, the most common double helical structure found in nature, the double helix is right-handed with about 10–10.5 base pairs per turn. The double helix structure of DNA contains a major groove and minor groove.

Detailed explanation-4: -A single helical turn of the DNA stretches over a distance of 34 angstroms, which means that there are 10 base-pairs in a single turn. Since the DNA turn represents 360 degrees and there are 10 base-pairs in one turn, that means each base-pair turns the DNA helix by 36 degrees.

Detailed explanation-5: -The length of 10 pairs of DNA is 34∘A. Therefore if DNA contains 1000 base pairs its length would be 3400∘A.