There are indeed three letters in the abbreviation "DNA" itself (more properly Deoxyribonucleic Acid), but then there are 6 letters in the word "binary". It terms of its contents, DNA has a spine made out of S and P (sugar and phosphate groups) and four variable bases: A C, G and T (adrenine, cytosine, guanine and thymine). So in terms of code, DNA has 4 variable characters, not 3. But otherwise, yeah, that is kind of interesting in a Matrix sort of way.