Re: Genetic or Epigenetic: The Causal Basis of Evolutionary Change

On Feb 20, 10:45 pm, CNCa...@xxxxxxx wrote:
On Feb 20, 6:56 pm, "rnor...@xxxxxxxxx" <rnor...@xxxxxxxxx> wrote:





On Feb 20, 3:15 pm, Ernest Major <{$t...@xxxxxxxxxxxxxxxxx> wrote:

In message
<3bfce55b-3c0e-4dca-8709-777ee0d5d...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"rnor...@xxxxxxxxx" <rnor...@xxxxxxxxx> writes

There are known behavioral mutations in Caenorhabditis and Drosophila
especially, but also in other arthropods and gastropod molluscs.  It is
true that the details by which genes specify neural circuits is still
murky and very incomplete, but this is a difficult area to investigate.
Certainly there is no reason to suspect that somehow the organization
of molecules withing the unfertilized egg carries the information
necessary to determine these circuits and behaviors.

Am I correct in recalling that nervous system development in
Caenorhabditis elegans is deterministic, and that variants in the
development path and final state are associated with genetic variants?

You are absolutely correct.  Every adult individual has exactly the
same number of cells in exactly the same configuration.  Every cell
devision is determined, including every cell predestined to die in the
process.  That is why it is such a valuable model organism for study.
That is especially why Brenner chose it to study the genetics of
neurobiology.  See,
 http://www.wormbook.org/chapters/www_specnervsys/specnervsys.html
for information on the "Specification of the nervous system".  As that
paper says about C. elegans: "Its cellular complexity makes the C.
elegans nervous system a prime model system to study a central
question in developmental neurobiology, namely how neuronal diversity
is genetically programmed."  Our friend here doesn't know about this,
or perhaps simply disbelieves in it.

There is also
  From gene to identified neuron to behaviour in Caenorhabditis
elegans.
  Rankin CH.
  Nat Rev Genet. 2002 Aug;3(8):622-30

Unfortunately, that doesn't seem to be available for free online, not
even an abstract.

I have read  that article and I can tell you that there is nothing of
the sort you are expecting in that aricle. It is a relatively short
review that in author's expression illustrates  " the power of using
the worm" to study behaviour".
It speaks about the role of proteins synthsiszed by genes in  neuron
structure, in structure of ion channels, etc. the importance of gene
mutations in knowing the functions of neurons. As is to be expected it
shows how mutations in genes cause defects in neurons and in the
neural circuits such as  loss of specific sensory behaviors, reduction
of the capacity of glutamatergic neurons to produce glutamate, delayed
pharyngeal relaxation, shortening of pharyngeal contraction, loss of
response to  nose-touch, defects in axon structure, etc. Then it
describes in some details the neural determination of  egg laying in
C. elegans, neural determination of habituation, identification of the
role of single neurons in specific behaviors, Innervation of pharynx
and its role in feeding behavior. Finally it describes  use of genetic
methods  of study of gene function in the nervous system of the worm.
In short, the review is irrelevant to the issue (which seems to be
forgotten.

You seem to argue that if physiology helps determine some aspect of
growth and development then that proves epigenetics is involved
because physiology is not genetics and therefore must be epigenetics.
And you seem to argue that if the nervous system helps determine
physiology, then the epigenetic information must be contained or
produced by the nervous system since nervous systems are specialized
to process information. Then you take a paper describing in intimate
detail just how nervous systems are produced and determined by gene
action but dismiss it as irrelevant to the issue.

My overall impression, based on weeks and months of back-and-forths is
that you take good science and completely reinterpret it on the basis
of what you mistakenly call "epigenetics". Yes there are all sorts of
things going on in the workings of the daily life and in the life
history of an organism. You fail to recognize that genetics lies at
the base of it but is far removed from the final process. Therefore
you dismiss genetics entirely.

You also completely misinterpret the process by which we learn about
genetics. The most easily seen demonstration of the work of genetics
is by disrupting that work with some mutation. Hence all those
mutations which cause "deficit" or "loss". Those are not at all
irrelevant; the proof of loss of function by altering a gene is proof
(or part of the proof, at least) of the function of the gene.

You also completely misinterpret the process by which we learn about
nervous system function. Ultimately, the nervous system is
responsible for behavior but the means by which it performs this
action is by producing proteins, by the work of ion channels, by the
capacity to produce glutamate, ..., all seemingly low level detail
which you downgrade and dismiss. The work of the genes in determining
nervous systems is exactly in these molecular level details. Then
the nervous system as a whole is responsible for producing behavior.
There are not genes "for" a particular behavior but there sure are
genes for things like ion channels and cell-cell recognition and the
like. Still you insist somehow that the nervous system rises above
genetics to include some sort of voodoo process of "epigenetics".

Yes, physiology works on a higher level of biological organization
than the genes. There are processes at work in physiology that are
best understood in system terms than by pure reductionism to see what
the molecules are doing. I have long fought with the molecular and
biochemical reductionists to insist on the holistic view of
physiological processes. But there is no denying that, at the base
of it all, lie the genetic and molecular biological machinery of the
cell just as there is no denying that, at the base of it all, lies
quantum electrodynamics or whatever else the physicists think up as
the theory of all theories.




.

Relevant Pages

  • Re: COMPARATIVE VERIFICATION OF A GENETIC AND AN EPIGENETIC MODEL
    ... by signals from the parental central nervous system. ... in which parental transcripts are deposited in the ovum under CNS ... central nervous system, without changes in genes, induces ... (i.e. "make the transcripts in the ovum, but not in other cells"). ...
    (talk.origins)
  • Re: Theory On Certain Functions Of Nervous System
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    (talk.origins)
  • Theory On Certain Functions Of Nervous System
    ... serve the genes which developed them; ... subsystems and parts of the body for adapting to new environments or ... So, sensory nervous system is an instrument that serve the genes, ...
    (talk.origins)
  • Theory On Certain Functions Of Nervous System
    ... serve the genes which developed them; ... subsystems and parts of the body for adapting to new environments or ... So, sensory nervous system is an instrument that serve the genes, ...
    (sci.bio.evolution)
  • RACE and Medicine
    ... differ in genes that impact health, they of course will be expected to ... As Jon Entine wrote in "Why Race Matters in Sports" on his website: ... unfairly stigmatize some patients and lead to inferior health care. ... Stephens, vice president for genetics. ...
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