Re: Article: Birds of a feather not related to each other

From: CNCabej (cncabej_at_aol.com)
Date: 12/15/04 

Date: Wed, 15 Dec 2004 06:02:49 +0000 (UTC)

J. Edser wrote:
>> CNC:-
>> This example shows how bird morphologies converge while their
>> genes diverge.
>> Nature is plainly telling us that evolution (of those morphological
>> convergences) doesn't depend on genes.
>
>JE:-
>I agree that a level above the DNA/RNA level
>may exist within multicells. These will probably be
>proteins. Prions have pointed the gun and cocked

I agree, but proteins, including prions, need themselves to be regulated. They
don't know when, where (or how long) to turn off/on. But the fact that living
systems, unicellulars and multicellulars exist for more than three billion
years means that they have solved this problem. And, in principle, we know
how: they have their own control systems. The Watson-Crick system of heredity
is a control system (in fact any hereditary, by definition, is a control
system) with the source of informatio (the genome), channels of information
flow and feedback loops of numerous regulatory circuits discovered from 60es of
the 20th century and on. By regulating the protein biosynthesis that system
accounts for most (not all as Sonneborn et al have shown) molecular characters
in unicellulars.

With multicellulars the problem is quite different. Proteins are not building
blocks of multicellulars, cells are (as shown akmost 2 centuries ago by
Schleiden and Schwann), several trillion differentiated cells of almost three
hundred types in our human body, arranged in strict spatial realtionship to
each other. Neither genetic code or genetic information nor the sequence of
amino acids in proteins have such an information (if they would have
multicellulars would arise soon after the emergence of life on earth and it
would not take more than 2 billion years to evolve).

Erection of such highly ordered entropy-resisting structures as multicellulars
are absolutely needs specific information.

In analogy with unicellulars we have to look for a control system in
multicellulars, and in analogy with unicellulars that system could also serve
(the Watson-Crick system is both the control system and the hereditary system )
 as an epigenetic system of heredity.

Let's return to your example. Prions, like other nonhousekeeping proteins are
necessary for various functions. Their expression is regulated by Ras proteins
(sometimes e.g. via another protein, Mks1). But Ras are proteins, and they also
need signals (=information) about when and where to be activated. We know that
this signal often comes from glucocorticoids of the adrenal gland. In turn,
adrenal production of glucocorticoids is a downstream element in a signal
cascade
along the hypothalamic-pituitary-adrenal gland. In fact the signal cascade
starts in the nonhypothalamic brain.

This is the case with expression of all the nonhousekeeping genes in our body
(hormones, growth factors, secreted proteins, neurotransmitters, neuropeptides
etc.)

Can brain know when and where in those trillions of cells of our body a gene
mustbe activated?. Since it does it can and it can because the pervasive
presence of the nervous system in the metazoan body allows it to receive
information on the state of the system and its immense computational capability
allows it to detect deviations from the set points it determines and via the
signal cascades send signals for restoring the deviant structures and
functions.

Let's prevent the anticipated counterargument: all the information for starting
signal cascades in the CNS is computational, nongenetic, hence epigenetic by
origin.

 
>it and the inheritance of stable acquired characters
>via experimentally altering cilia patterns in
>protists by Sonniborn et al has fired the gun. So far
>such events have not been documented within multi-
>cellular organisms.

Cases of transgenerational inherited characters developing in the offspring of
rotifers and insects (and are transmitted for numerous generations even in the
absence of the environmental factor that induced them initially) are also
known.

Thank you.

Nelson R. Cabej

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