Definition of Double helix

1. Two strands of DNAcoiled about a central axis, usually a right-handed helix. The two sugar phosphate backbones wind around the outside of the bases (A = adenine, G = guanine, T = thymine, C = cytosine) and are exposed to the solvent. The strands are antiparallel, thus the phosphodiester bonds run in opposite directions. As a result the structure has major and minor grooves at the surface. Each adenine in one strand of DNA is hydrogen bonded to a thymine in the second strand; each guanine is hydrogen bonded to a cytos