1. DNA is made up of deoxyribose, phosphate groups, and four nitrogenous bases (adenine, guanine, cytosine, thymine). 2. The bases pair up through hydrogen bonding between complementary base pairs (adenine with thymine, cytosine with guanine). 3. The paired bases and sugar-phosphate backbone form the structure of the DNA double helix, with the bases in the middle and the backbones on the outside.