Subject: Re: On influencing factors
Date: Sun, 1 Nov 98 14:35:00 -0600
From: Mark Mills <mmills@fastlane.net>
To: "Memetics List" <memetics@mmu.ac.uk>
Message-Id: <E0za4BA-00022z-00@dryctnath.mmu.ac.uk>
Derek,
>> Do you suggest outside influences are immaterial to cellular
>> differentiation?
>
>I wouldn't say immaterial, but I would say much less important. The
>geno-pheno correspondence is, as Waddington used to say, canalized
>(Gatherer 1996), meaning that it's rather like running a ball bearing
>down a grooved landscape. The ball bearing will tend to get into one
>groove and stay in it. Extreme environmental conditions could cause it
>to pop out of one groove and into an adjacent one, but most of the
>time it will stay within the groove it starts out in.
I don't mind the ball and groove analogy. I'm not sure what you mean by
'extreme environmental conditions,' though.
'Extreme' suggests 'abnormal,' and that's not my interest. I'm
interested in common next neighbor interactions. My interest is this:
to what degree is gene expression in one cell triggered by the behavior
of neighboring cells. I hope you see the parallels for memetics.
Everyone knows that certain kinds of cells can kill other cells. It is
also clear that the lack of proximal red blood cells will kill cells. It
is also clear that during epigenesis, millions of cells die to complete
an organ's differentiation (brain and skeleton come quickly to mind).
These examples are macroscopic to the cellular processes, though.
Everyone knows the ingestion of carcinogens (an outside influence) often
leads to 'improper' gene expressions. Unfortunately for my argument,
carcinogens damage the DNA. This is more along the lines of your
'extreme conditions' than my 'normal cellular interaction.'
Maybe you can clarify this. All I can do is suggest extra-cellular
triggers are normal.
This 'locus of control' conversation is critical to memetics.
I suspect many will be a bit uncomfortable with extra-cellular genetic
triggers. Such a phenomena would diffuse the locus of control and cause
a variety of philosophical problems.
>> If both cellular rhythms and protein production can be influenced by
>> forces outside the cell, how clearly can we draw the boundary between
>> what is controlled by DNA vs 'the outside.'
>
>They are influenced by outside forces, but never in such a way as to
>cause a differentiated cell to de-differentiate. Once a cell loses its
>toti/pluri-potency there is no going back. Neurons respond extensively
>to things like nerve growth factor, neurotransmitters etc, but they
>always stay neurons.
I have no problem with this. Nothing in my perspective requires
epigenesis to be reversible.
Mark
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