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To: js1138
In fact it has been explored for over a hundred years, and no one has observed a pattern in which mutation anticipates need in any statistical manner

I don't know exactly what you mean by anticipation in terms of cellular activity, but I do know that Dr. James Shapiro explains some non-stocastic mutations here.

A 21st Century View of evolution

The conventional view is that genetic change comes from stochastic, accidental sources: radiation, chemical, or oxidative damage, chemical instabilities in the DNA, or from inevitable errors in the replication process. However, the fact is that DNA proofreading and repair systems are remarkably effective at removing these non-biological sources of mutation. For example, consider that the E. coli cell replicates its 4.6 megabase genome every 40 minutes. That is a replication frequency of almost 2 kHz. Yet, due to the action of error-recognition and correction systems in the replication machine and in the cell to catch mistakes in already-replicated DNA, the error rate is reduced below one mistake in every 1010 base-pairs duplicated, and a similar low value is observed in mammalian cells (32). That is less than one base change in every 2000 cells, certainly well below the mutation frequencies I have measured in E. coli of about four mutations per every 100 to 1000 cells.

In addition to proofreading systems, cells have a wide variety of repair systems to prevent or correct DNA damage from agents that include superoxides, alkylating chemicals and irradiation (33). Some of these repair systems encode mutator DNA polymerases which are clearly the source of DNA damage-induced mutations and also appear to be the source of so-called "spontaneous" mutations that appear in the absence of an obvious source of DNA damage (34). Results illustrating the effectiveness of cellular systems for genome repair and the essential role of enzymes in mutagenesis emphasize the importance of McClintock?s revolutionary discovery of internal systems generating genome, particularly when an organism has been challenged by a stress affecting genome function (Fig. 4; 5).

McClintock recognized that genetic change is a cellular process, subject to regulation, and is not dependent on stochastic accidents. The idea of internally-generated, biologically regulated mutation has profound impacts for thinking about the process of evolution. Darwin himself acknowledged this point in later editions of Origin of Species, where he wrote about natural "sports" or "...variations which seem to us in our ignorance to arise spontaneously. It appears that I formerly underrated the frequency and value of these latter forms of variation, as leading to permanent modifications of structure independently of natural selection." (6th edition, Chapter XV, p. 395).

And your questions were trivial.

793 posted on 04/07/2008 12:27:05 PM PDT by AndrewC
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To: AndrewC

Masciarelli
I’m curious about “their non-random operations.” Does ‘non-random’ suggest that the very instructions for all possible morphological changes are front loaded or pre-programmed into living things, needing only a given catalyst to get things going?

James Shapiro
No. Non-random means that they operate under certain conditions (e.g. after genome damage or viral infection) and that these systems make characteristic kinds of changes. When a retrovirus-like element inserts in a new genomic location, it carries with it a defined set of regulatory signals that can affect the reading of nearby DNA sequences in very particular ways. This is an example of non-randomness. In addition, some changes (such as those in the immune system) can be targeted to specific locations by the presence of particular signals in the DNA or by activation of transcription. These phenomena show us that cells are capable of altering their genomes in non-random but not rigidly specified or pre-determined ways.

http://www.iscid.org/james-shapiro-chat.php


797 posted on 04/07/2008 12:56:52 PM PDT by js1138
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