[kaba0]

I did think about that, that’s why I added the second paragraph, namely that what about RNAs? (Since presumably they precede the DNA world) They can self-bind (I don’t know the proper nomenclature in English), but by all means they have 4 bases.

[WClayFerguson]

There's two kinds of base pairs, is identical to there's 4 kinds of bases.

[kaba0]

RNAs are a single chain. Your point makes no sense.

A code with a 4 letter alphabet would be 2 letter, if it happened to use a parity “bit” or other error correction info?

[WClayFerguson]

I never said RNA was built on two types of molecules. I said DNA was.