DNA is a macromolecule that is critical for life. Much of the functionality of DNA lies in itscomplex structure. What are the 2 main forces responsible for holding together the structureof DNA and what does each force hold together? Solution The double helical structure of DNA (deoxyribonucleic acid) is formed by the coiling of two polynucleotide chains, similar to a spiral staircase. Of the two polynucleotide chains, the sugar-phosphate backbones are exposed to the outside of the spiral staircase. While the base pairs (side chains) extend towards inside of the helix. The two strands are connected together by hydrogen bonds and hydrostatic forces. Of the two polynucleotide chains, the sugar-phosphate backbones are exposed to the outside of the spiral staircase. While the base pairs (side chains) extend towards inside of the helix. The two strands are connected together by hydrogen bonds..