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******** This is the last one of my first series of responses to the
contributions in the thread "What does the creation lack?" ********
I have not responded to George Murphy's mailings of 30 Oct, 2:48 PM, and
31 Oct, 07:39:41 -0500, nor to Wayne Dawson's of 30 Oct, 20:09:50 EST,
because I fully agree with them.
My further postings will deal with some of the later contributions.
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bivalve wrote:
>
> The latest Nature has an article related to the issue of the probability of a particular complex biomolecular structure evolving: Salehi-Ashtiani and Szostak. 2001. In vitro evolution suggests multiple origins for the hammerhead ribozyme. Nature 414:82-84. This structure occurs in a wide variety of organisms. It turns out to be the commonest and simplest way of making the needed structure in vitro. This suggests that the probability of "undirected" evolution "happening" upon it (i.e., through ordinary providence) seems relatively good.
>
> Dr. David Campbell
> Old Seashells
> 46860 Hilton Dr #1113
> Lexington Park MD 20653 USA
> bivalve@mail.davidson.alumlink.com
In vitro RNA evolution cannot be compared with natural protein
evolution, as I discussed earlier on this list. In RNA evolution, the
same molecule is both genotype and phenotype, i.e. selection tests a
mutation either immediately or at the will of the experimenter, and each
and any nucleotide can be selected individually. In natural protein
evolution, on the other hand, there is translation between genotype and
phenotype, implying selection not of an individual mutated nucleotide,
but of a mutant organism characterized by a mutated triplet, where
silent positions are ignored, and only a part of the other possible
amino acids are accessible by single-step mutations; furthermore,
fixation of an adaptive mutation is a long, risky path, particularly in
diploid organisms. All this has the consequence that probabilities
estimated in in vitro RNA evolution are virtually irrelevant for natural
evolution. In any case, they are very much too high.
Peter
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