Each person has a unique set of chemical blueprints that determines how his or her body looks and functions. These blueprints are contained in a complex chemical called deoxy-ribonucleic acid (DNA), a long, spiral-shaped molecule that's found inside each body cell. DNA carries the codes for genetic information and is made of linked subunits called nucleotides. Each nucleotide contains a phosphate molecule, a sugar molecule (deoxyribose), and one of four coding molecules called bases (adenine, guanine, cytosine, or thymine). The sequence of these four bases determines the genetic code.