There are only four molecules in the DNA chain: adenine (A), guanine (G), thymine (T) and cytosine (C). These As, Cs, Ts and Gs are also called "bases." These four molecules partner: C partners with G and T partners with A. Pairing is a natural state for DNA and if you pulled the double helix apart, it would inevitably move back together, like two long chains of magnets that are attracted to each other.