On Tue, 9 Mar 2004 "John Edser" wrote: 

NC (is NC you correct initials?):
>>Thus, you agree that the expression of nonhousekeeping genes, which are
>>responsible for cell differentiation and cell-cell interactions, is under
>>epigenetic (NONGENETIC) control.

JE:-
>Yes. Note however that epigenetic products are
>ultimately coded for by genes. 

N.C.
This is correct and I agree since it implies that the epigenetic information
controls and USES genes as specialists for synthesizing proteins what is
another way of saying that gene expression is under control of the epigenetic
system.

JE:
>"Everything" can be reduced to just genes when reductive reasoning
>(deduction) is misused. 

N.C. 
No use will come out of that misuse. Trying to reduce epigenetic in formation 
to "just genes" would be no more logical than claiming, e.g. that
the genetic
information is ultimately a property of nitrogen bases, sugars or phosphates or
the atoms (why not elementary particles, then?) which they consist of, and not
of the DNA.

NC:-
>>In the view of the fact that all the stages metazoan reproduction
>>(gametogenesis, early development and organogenesis)
>>depend on cell differentiatiion, it follows that this epigenetic system, or
>>these "epigenetic control hierarchies", regulates the
individual development
>>in metazoans.

JE:-
>It is a classical "chicken and egg" argument.
>The CNS regulates genes but genes code for the
>CNS. So what came first, the genes or the CNS?
>The answer is neither. They evolved _together_
>within a _single_ unit of selection.


N.C.
It would be a "classical "chicken and egg" argument"
only if the premise 
"genes code for the CNS" would be real, which remains to be proven.  
It is impossible for me to imagine how "genes code
for the CNS". Where is the knowledge on which this statement is based?
If I am right, to code for the CNS means to give instructions how to put it
together.
Has anyone ever presented a hypothesis on how genes code for the CNS? No, and
for good reasons. Because such an attempt is related to at least two formidable
problems.
First, one has to answer, however hypothetically, "How?" the DNA
or genes might
set up such a complex structure as the CNS. The only kind of information genes
contain is determined by their specific sequence of nucleotides that makes
possible  the synthesis of a specific protein etc. After half century of
unprecedented intensive studies on gene function we do not REALLY know of
anything else a gene can do.

Second, for the sake of the argument, let's suppose that genes might somehow
manage to give instructions for assembling  the CNS. Another equally formidable
difficulty would arise: several billion bits of information contained in the
whole DNA 
of vertebrates represent only a tiny, litterally negligible, fraction of the
information needed for setting up a vertebrate brain.

JE:-
>Epigenetic systems of inheritance have been
>documented within nature. The problem is,
>how do you experimentally separate out Mendelian
>gene inheritance from an epigenetic level
>of inheritance? 

N.C.
If we admit that "Epigenetic systems of inheritance have been documented in
nature" then we have to determine the relationship of this system to other
systems, including the genetic system of heredity, which in metazoans
(multicellulars in general) is the main determinant of heredity at the level of
the cell. The epigenetic system of heredity is a  hierarchic systems as
visualized in signal cascades. A signal cascade shows that the ultimate control
of gene expression is information that is generated in the CNS (it is not
inherited, but computated in the CNS what seems to be the evolutionary solution
of the impossibility of transmitting  the tremendous amount of information for
building a metazoan structure via gametes).
As for the Mendelian gene inheritance, in my view, there is no special problem
of separating its relative role from the "epigenetic inheritance". Metazoan
heredity is function of a hierarchical control. While the role of each element
is determined by its relative position in the hierarchy, the metazoan heredity
is one and indivisible.  

JE:-
However for the gene centrics that dominate this site
most will just falsely conclude that in the end,
it is all just reducible to genes.

N.C.
They have not done it so far. Let's hope they will, and I would be really
curious to see how could one (analytically, not rhetorically by unsubstantiated
statements) reduce the epigenetic information generated by a computational
processing in the brain to genes.

JE:-
I think a good strategy would be to create a hot
list of documented heritable epigenetic events
and post it to sbe for comment.

N.C.
I hope to do something like that very soon.

Thank you.
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