lukesg at frb.gov
lukesg at frb.gov
Mon Feb 22 11:16:10 EST 1999
Another Darwinian process of increasing complexity, I find interesting and
that is easier to study experimentally, is the embryonic development of the
brain. Until recently it was assumed that genes contained the control
information for structuring brain development. While I don't know the
results of the latest research, my impression is that researchers now think
that the developmental structure of the brain, that distinguishes different
species, does not come primarily from genetic coding. Instead it come from a
Darwinian process involving an extensive overproduction of generic neural
growth, which is sculpted (through selection) into specific structures by
massive cell death. This detailed wiring and structuring of the brain is
controlled by local conditions and competitive processes not directly related
to genetic programming.
Amazingly, when neural cells are transplanted from one part of the brain to
another or even from one species to another, they do not develop in a pattern
consistent with their source, but develop in a pattern consistent with the
other cells in their new surroundings.
However, if these self-organizing processes are highly dependent on the
specific nature and informational depth of these local organic processes, it
may be difficult to simulate them on a digital computer, or even come up with
linear functional relationships or logical rules for modeling it in detail.
In article <7akpi4$bam at net.bio.net>,
Richard Gordon <gordonr at cc.UManitoba.CA> wrote:
> >In article <7aeppq$kto at net.bio.net>,
> > "SH at OLIN©" <W.J.Koning at chem.uu.nl> wrote:
> >>> "What processes make DNA MORE complicated?"
> I would be interested in any speculation that anyone (especially Dick and Ed)
> have on what processes might be involved.
> Okay, I'll try to summarize my 1800p. book in a few sentences:
> 1) The genetic program consists of an hierarchical alternation of physical
> waves traversing portions of embryonic tissues and the gene cascades they
> set off.
> 2) The genetic program thus may be described as a differentiation tree.
> 3) The differentiation tree maps onto the linear genome (the DNA).
> 4) Chromosome rearrangements (including sizable duplications) can sometime
> produce viable organisms, still capable of finding a mate, with more
> complex differentiation trees.
> 5) It is, perhaps for various reasons, easier (more usually viable) to
> enlarge a differentiation tree than prune it.
> 6) Some differentiation tree lineages therefore have more and more complex
> differentiuation trees = progressive evolution. QED
> Yours, -Dick Gordon
> Dr. Richard Gordon, Radiology, U. Manitoba, HSC, 820 Sherbrook Street,
> Winnipeg R3A 1R9 Canada, Phone: 204-789-3828/The Hierarchical Genome &
> Differentiation Waves: Novel Unification of Development, Genetics &
> Evolution: http://www.wspc.com.sg/books/lifesci/2755.html
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