The two molecules that make up the sides / backbone of the dna double helix are

it has an alternating chemical phosphate and sugar backbone, making the 'sides' of the ladder. (Deoxyribose is the name of the sugar found in the backbone of DNA.) In between the two sides of this sugar - phosphate backbone are four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).