"TomHendricks474"  wrote in message
news:c9lduo$2vv8$1{at}darwin.ediacara.org...
> > As far as anyone knows, the choice of chirality is arbitrary.
>
> Many theorise that it is not arbitrary:
> http://www.abc.net.au/science/news/stories/s924661.htm >>
>
> This one suggested Serine pushed
> all the other amino acids into a specific chirality
> much like a alpha male dancer pushes females
> into certain arm positions. Interesting.
>
> I looked up the coding for Serine (the most 'observered frequency" of all
amino
> acids according to a chart from Non Darwinian Evolution, King, L.L. in
Science
> 16, May 1978)
>
> And noted that it has 6 ways to be coded.
> AGA (all purines)
> AGG (all purines) or
>
> UCU (all pyrimidines)
> UCC (all pyrimidines) or
>
> UCA (pyr, pyr, pur in wobble) or
> UCG (pyr, pyr, pur in wobble)
>
> Though I don't have an exact point,
> I note the coding seems to really
> be almost all purine, or all pyrimidine, and with my recent
> ideas, that seems to fit in there
> somewhere - sort of.

It is important to realize that the code is not completely frozen.
It has evolved.  Here is a good, though not particularly recent, review:
http://www.pubmedcentral.gov/articlerender.fcgi?artid=372862

My guess would be that the AG? block of codons is not primitive;
serine and arginine are invaders.  What was there originally?
Maybe glycine, maybe nothing.  My guess is that it is an amino
acid that has since been lost from the code.  Since lysine and
arginine are probably late-comers, we need another diamino acid.
How about NH2-CH2-CHOH-CHNH2-COOH?  Later, after lysine and arginine
were available, it was no longer needed.  (Very hydrophilic, as
you can see.  I'm sure that makes you happy.)
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