[exDemMom]

I doubt that they would form any codons at all, since the tRNAs bind to specific codons. They could bind tRNAs, I suppose, if they had the same H bond patterns on their edges as natural DNA bases. But then, why would one need non-naturally occurring bases?

If you wanted to create a whole genetic system—the base pairs, tRNAs that recognize the triplets, enzymes to charge the tRNAs with novel amino acids—I suppose that is possible as an academic exercise. Not sure how useful it would be.

[grey_whiskers]

OK, so I skipped a step. My point was solely that the presence of alternative DNA base pairs isn't even half the battle: in particular, would the two sets of 4 base pairs, each have their own sets of tRNA (and then amino acids)? If they mixed and matched would the amino acids be the original set, or would there exist new amino acids which bonded more strongly to the tRNA than the existing amino acids?

Would there be any interesting 2^o structures in the proteins from any new amino acids (etc. etc.)

All of which is to say something of a sensitivity analysis on the system as it exists, is the optimal or near optimal for forming animal/human proteins, compared to other, umm, ingredients (assuming the same general form DNA--> tRNA --> amino acid --> protein)?

...and would the current proteins which unzip and stabilize DNA (and correct mistranscriptions) work as well on the DNA with 8 base pairs?