dna
DNA Double-Helical Structure DNA has a double-helical structure Figure 2.23 . It is composed of two strands, or polymers, of nucleotides. The strands are formed with bonds between phosphate and sugar groups of adjacent nucleotides. The strands are bonded to each other at their bases with hydrogen bonds, and the strands coil about each other along their length, hence the double helix description, which means a double spiral.