# Advantageous properties of 4 letter alphabet (in DNA)?

As you know DNA is composed of strings of 4 letters. I am wondering if the number 4 here has any significance? Any property of 4 that makes using 4 letters more advantageous over more (or less) letters to encode information?

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I'm no expert, but I would expect the answer to be chemistry or biology and not mathematics. The four letters correspond to certain acids, and so it's not simply an encoding, but also has a functional part. –  Helge Jul 18 '10 at 10:49
I'm no expert either, but to me this looks a lot more like numerology than biology or chemistry, let alone mathematics. –  Franz Lemmermeyer Jul 18 '10 at 12:02
Also, there are technically more than four bases - there are less common modified bases, such as m5C. See en.wikipedia.org/wiki/Nucleobase. –  Thomas Bloom Jul 18 '10 at 12:10
If you believe in the RNA world, this probably originated as some sort of compromise between having a minimally complex chemistry with sufficiently interesting enzymatic/catalytic behavior. –  Rob Grey Jul 18 '10 at 12:49
There might also be a genome-compactness/efficiency vs. chemical complexity/difficulty-of-error-correction argument. –  Rob Grey Jul 18 '10 at 12:52

A 1993 PRL by Hornos and Hornos suggested that the evolution of the genetic code manifests itself through symmetry breaking. According to them the basic symmetry is supposed to be $SU(2)^{\otimes 3}$ (three nucleotides per codon).