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Evolvability is testable

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In the following article, ask yourself if “the protein tape of life may be largely reproducible and even predictable,” what this means for the testability of evolutionary theory and ID should nature be constituted so that no Darwinian pathways exist for certain proteins.

Darwinian Evolution Can Follow Only Very Few Mutational Paths to Fitter Proteins
Daniel M. Weinreich, Nigel F. Delaney, Mark A. DePristo, Daniel L. Hartl

Five point mutations in a particular ß-lactamase allele jointly increase bacterial resistance to a clinically important antibiotic by a factor of 100,000. In principle, evolution to this high-resistance ß-lactamase might follow any of the 120 mutational trajectories linking these alleles. However, we demonstrate that 102 trajectories are inaccessible to Darwinian selection and that many of the remaining trajectories have negligible probabilities of realization, because four of these five mutations fail to increase drug resistance in some combinations. Pervasive biophysical pleiotropy within the ß-lactamase seems to be responsible, and because such pleiotropy appears to be a general property of missense mutations, we conclude that much protein evolution will be similarly constrained. This implies that the protein tape of life may be largely reproducible and even predictable.

http://www.sciencemag.org/cgi/content/full/312/5770/111

Comments
"Pervasive biophysical pleiotropy within the ß-lactamase seems to be responsible, and because such pleiotropy appears to be a general property of missense mutations, we conclude that much protein evolution will be similarly constrained." The 'biophysical pleiotropy' they're talking about here, from the paper, appears to mean that the protein products of various missense mutants end up 'interacting' with other proteins/chemical compounds that make up the cell in such a way as to minimize the 'resistance' that will be 'selected' for. This, in turn, would seem to mean that in the 'biophysical' world, only certain protein 'configurations' are functional. And that's why the authors conclude the paper by saying: "It now appears intramolecular interactions render many mutational trajectories selectively inaccessible, which implies that replaing te protein tape of life might be surprisingly repetitive. It remains to be seen whether intermolecular interactions similary constrain Darwinian evolution at larger scales of biological organization." This is an important finding. And I'm a little disappointed that this board hasn't done a better job of wrestling with its implications. I think Dr. Dembski's question at the head of this post is pertinent. The link to the article is in #2 above.PaV
April 10, 2006
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Here's a link to the article. I just printed it out myself. http://www.oeb.harvard.edu/hartl/lab/publications/pdfs/Weinreich-06-Science.pdfPaV
April 8, 2006
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Can anyone translate the words "pleiotropy" and "missense" as they relate to this sentence? I think that I am missing the full impact of this.

"Pervasive biophysical pleiotropy within the ß-lactamase seems to be responsible, and because such pleiotropy appears to be a general property of missense mutations, we conclude that much protein evolution will be similarly constrained."

They seem to be saying that if you can't find a straightforward Darwinian pathway from protein A to protein B because a) there are too many non-neutral (missense) point mutations involved b) all the stepwise paths from A to B have intermediates that would be discarded by natural selection then c) presume that the gene in question is part of the specification for more than one protein and/or phenotypic (pleiotropy) product so that the untenable intermediate missense mutations impart a selection advantage with one of the alternate products.

This is a wonderful example of yet another ad hoc hypothesis being deployed to prop up the most failed theory in the history of science.

idnet.com.au
April 7, 2006
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