Re: How do cells know if they're a skin cell, blood cell, etc...
From: CNCabej (cncabej_at_aol.com)
Date: 02/05/05
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Date: Sat, 5 Feb 2005 13:46:32 -0500 (EST)
Perplexed in Peoria wrote:
corey wrote:
>what makes some cells function >differently than others? My theory is that >it
has something to do with your brain >telling it what to form, but Im not fot
sure. >Anyone know?
PiP:
> various chemicals within the cell interact with the
>genes in order to determine which genes should be "expressed"
>(i.e. be used to make proteins) in which cells. Different
>genes are expressed in skin vs blood, leaf vs petal.
>
NC:
However, the question remains unanswered: why different chemicals interact in
different cells to make them different types of cells. (all of them come from
a single cell (zygote) and always are genetically identical).
>Where do these chemicals come from? Well, some of them
>result from "receptors" in the membrane of the cell, which
>can detect hormones and other chemical cues in the cell's
>environment, and then respond by making different chemicals
>("second messengers") inside the cell. It is these
>"second messenger" chemicals that actually interact with
>the genes.
NC:
Again you have to explain why different receptors are expressed in different
cells, before we talk about the role of hormones and second messengers. The
genetic identicalness of all cells makes impossible any genetical explanations.
There is no way you could avoid the omnipresent "ghost" of epigenetics.
PiP:
>I should add that not all of the information determining the
>cell's "fate" comes from outside. The cell also contains
>other chemicals which enable it to "remember" past decisions.
>Thus, the current decision to become a skin cell is partially
>determined by a past decision (made much earlier in development)
>to become an epidermal cell. And a chemical inside the cell,
>an "epigenetic factor", 'remembers' that past decision.
>
NC:
Now, we agree, but at this juncture we have to talk about the origin of the
epigenetic factors and the epigenetic information that by determining specific
spatio-temporal activation of NONHOUSEKEEPING genes determines cell
differentiation, the individual development, morphogenesis and organogenesis,
which is another way of saying determines metazoan inheritance at the
supracellular and organismic levels.
>Ok, moving back to the exterior of the cell, you may ask where
>do those "hormones and other chemical cues" come from.
>Well, it turns out that a recent poster to this NG, a Mr. Cabej,
>has been promoting an idea very much like your theory that
>the brain is involved. Maybe he is right. To learn more
>about Cabej's theory, search for "epigenetic" in this NG.
>
>But Mr. Cabej's theory, and yours, apparently can't answer my
>extended question regarding plants. Plants don't have brains.
NC:
My theory is intended to explain the metazoan heredity, which has been
impossible to be explained by the gene theory. By developing the Epigenetic
Theory of Heredity in Metazoans, I didn't feel that I had to necessarily deal
with the plant heredity (which also remains unexplained by the gene theory) for
the simple reason that, plants lack the epigenetic mechanism of METAZOAN
HEREDITY.
This is not to say that plants have not an epigenetic mechanism of heredity. As
I have predicted, the control system (still not sufficiently known) that
maintains the plant structure might well function as an epigenetic system of
heredity during their reproduction. This occurs in animals and there is no
reason why it would not work in plants.
And, finally, one should argue against my theory basically on what it deals
with not only on what it does not. I still am encouraging you and everyone
(especially genecentrists) here in sbe an outside to argue against or, better,
to show that the evidence I have presented in favour of my theory does not
prove, is irrelevant or even disproves it. Such input would be a really
constructive one.
Regards,
Nelson R. Cabej
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