A complex organism would have thousands of different DNA molecules. DNA is
made up of 4 bases (adenine, guanine, cytosine, and thymine) which are each
bonded to a sugar (deoxyribose) and a phosphate to make nucleotides. These are
repeated in various sequences along the molecule. Complementary bases pair to
form a double helix structure. The sequence of nucleotides makes a gene which is
used to make proteins.