Question

WHY IS THE SHAPE OF THE DNA SPIRAL TYPE? WHAT ARE THE RODS IN BETWEEN FOR?

Answer 1

In DNA, two polynucleotide chains are coiled to form a helix or spiral structure. Strands are wrapped plectonemically in a right handed helix. These strands are antiparallel i.e, one strand is oriented in the 5' --> 3' direction and other in the 3'-->5' direction. It is the angle of interaction between base pairs result in formation of major and minor grooves. This helix pitch (distance along the axis per 360 degree turn) is 33.2 A^o makes the shape of DNA spiral. Sugar phosphate forms backbone of this helix while nitrogenous bases (Rod shaped) project in wards to each other. These base pairs are in the inside of the molecule stacked close to each other.