dna is made up of molecules called nucleotides each nucleotide contains a phosphate group, a sugar group and a nitrogen base. the four types of nitrogen bases are adenine (A), thymine (T), guanine (G), and cytosine (C). Deoxyribonucleic acid or DNA is a molecule that contains the instructions an organism needs to develop, live and reproduce. These instructions are found inside every cell, and are passed down from parents to their children.