The four base molecules of DNA are adenine, thymine, cytosine, and guanine, or A, T, C, ang G. They act as trinary bits of information and in computing terms are known as codons. They are electrochemical in nature, unlike binary bits which are purely informational using electronic charge as a base, and therefore aren't typically considered compatible. However, active research in this area aims to bridge the nature of the two.
Roughly 1.5% of DNA strands consists of codons, which is enough for one strand to hold 0.2 Gb of information. Some applications are being considered for this fact. One is the alteration of DNA to program biological systems for better defenses against diseases, a field of research currently very far away from understanding how to reach this goal. Another is using DNA outside of biological systems as a base for liquid computing, as being researched by the Shanghai Jiao Tong University in China.
Imperial College London explanation of DNA computing functions and intentions
