"TomHendricks474"  wrote in message
news:c9qalb$1f62$1{at}darwin.ediacara.org...
> By the way, what is your opinion on dimers as being a part of selection
> pressure?

Tom, as I have said several times, and as several other people have
said, it doesn't even make sense to TALK about "selection" of
entities that do not reproduce.

As a stretch, it MIGHT make sense to talk about selection of a
chemical species that is continually produced pre-biotically,
but nucleic acids don't qualify, IMO.  Maybe you could convince
me that the bases are continually produced, or some simple
amino acids, but not polynucleotides.

If we are talking about reproducing naked genes, then maybe
there is some selection due to UV formation of dimers.  That
pressure would act against any duplex sequence that has
consecutive pyrimidines.  So, it would select for sequences
that alternate between purines and pyrimidines.

More strongly, it would be a selective force encouraging
any nucleic acid sequence that is not completely stupid
to get into the deep water and out of the sun.
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