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Originally Posted by eburacum45
My suggestion is that other possible associations of more exotic acids don't get a chance because these twenty and their derivatives out-compete them; and they can do this because of their association with DNA/RNA.
Do you think it possible then that other stable information-carrying molecules might exist? Any suggestions? If such molecules do exist they might not code for a biology using all the same amino acids as our own.
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My apologies- I didn't realize you were tying your speculation to DNA/RNA being the dominant genetic information carrier. I became confused when you started invoking that exotic amino acids had been "discovered" in meteorites.
Yes, there could well be another information carrier besides a single or double- stranded DNA/RNA. But interaction with amino acids to make proteins has about zero to do with the genetic information containted in a cell. Sure, even in archaebacteria, there is replicase and other enzymes that work directly with the genome, but the vast number of proteins are synthesized in the cytoplasm, with little help from the "phonebook" DNA genome, besides a mRNA crib note.
It is the proteins that are seen to do, and make structures- it is their interactions that could build a better enzyme, or potentially lyse the cell. For a time, before Watson & Crick, some biologists believed that proteins were the cellular structures that carried the genetic code, simply because of how detailed they could be, and how chains could interact and "fold" within themselves.
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Originally Posted by eburacum45
Or, alternatively, other information carrying molecules might code for a biology remarkably similar to our own. It is certainly possible that the association of proteins and amino acids that we have on Earth is the simplest and most optimised for survival;
but we have only a sample of one to go on.
If all life on Earth descends from a very small initial sample, then the common features might be a result of that limited ancestry rather than a universal rule.
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Nature does favor simplicity- I would think certainly with a couple billion years under its belt, life on Earth would've had a chance to consume a 21st amino acid and incorporate it into a protein. But that amino acid chain was too complex, and interfered with the other amines, which are really very simple molecules. I don't deny that Earth life descends from a small sample- mitochondria and mitochondrial respiration essentially prove this. But in the end, I imagine the same 20 simple amino acids will be utilised on other worlds almost exclusively, and I'll bet you all of my Enron shares that this experimentation yields extremely few, if any, working proteins with a "bizarre" amine contained therein.