DNA encoding is slightly more complicated than a base four system. DNA uses triplets of four possible nucleotides (Adenosine, Cytosine, Guanine, and Thymine) to encode 21 different amino acids. However, the encoding has no frame of reference. That is, encoding can begin again shifted by 1 or 2 nucleotides. Additionally, the encoding is also represented on the reverse complement making a total of 6 frames of reference, and any or all may be valid. In a programmers world, this is like encoding a second (or third) program by shifting the starting op-code by 1 byte and getting another valid program. Even weirder, imagine shifting the start by 2 bytes, then taking the one's complement of the program and reversing the bit-order to get another valid program. We enforce encoding to have a definitive start, but DNA has no such restriction and allows for a much higher information content.