AP EAMCET Engineering 21 Sep 2020 Shift 2 Paper

(d) Watson and Crick proposed that DNA molecule is in the form of a double helix with two polynucleotide chains coiled around one another in a spiral. This is known as B-DNA or biological DNA. It has 10 nucleotides pairs per turn of the double helix and is right handed with a diameter of 20Å. One complete turn of the double helix is 34Å.The distance between adjacent stacks or nucleotides is 3.4Å.