IUBio

DNA and the neuron

r norman rsn_ at _comcast.net
Sat Sep 11 15:20:15 EST 2004


On 8 Sep 2004 14:41:40 -0700, rscanlon at nycap.rr.com (ray scanlon)
wrote:

>I am starting a new thread. "The liver and the brain" was overrun by
>trash talk.
>
>r norman writes:
> 
>> Neither development nor C. elegans are in my area, so I only know some
>> generalities.  The major feature is that environmental cues such as
>> pheromones or high temperature (27 C) can trigger a resting stage in
>> larval development, the Dauer stage or diapause.
> 
>(snip) 
>
>> Also, C. elegans is capable of associative learning, context specific
>> habituation, and other plastic changes in behavior.  This is not
>> development, but does illustrate that an animal that is so highly
>> constrained genetically also shows a learned component to its normal
>> behavior.
>
>NvN is with us forever. Very respectfully, I suggest a different view.
>The DNA survived. Therefore, we may say that it is structured to
>survive; the proof being that it survived. Fiddle-Dee-Dee.
>
>The DNA constructs a nervous system. The proteins that the DNA
>produced have the ability to modify the synapses that the proteins
>form. The proteins have the ability to extend axons, composed of
>proteins, and form new synapses. This is spoken of as a "learned
>component". The artificial distinction between the formation
>(continual) of the nervous system by the proteins and the modification
>(continual) of this nervous system by the proteins is an arbitrary
>academic exercise.
>
>DNA may have evolved that survived in the presence of other DNA
>molecules. We say that this DNA requires other DNA molecules to
>survive. This leads to the distinction between altricial and
>precocial, another academic exercise.
>
>The DNA that produced a nervous system that survived in a past
>environment produces the same nervous system. That today's environment
>closely matches the past environment is a glorious happenstance.
>
>Human DNA produces an altricial nervous system that is perfectly
>constructed to survive in its mother's arms (another DNA
>construction).
>
>Is this too extreme a view? Does it fail the pc test?	
>

Sorry to be so long responding -- I have been away from a computer.
There is a life to be lived outside of news groups!

Pc-ness has  nothing to do with it.  You have a point in that the
cellular mechanisms involved in modification of nervous systems
(plasticity) often show some general similarity to the cellular
mechanisms involved in development.  However most people do find a
useful distinction between nervous system structure and function and
the consequent behavior that is "preformed" or produced by factors
already present in the fertilized egg, the zygote,  and those
structures  and functions and behaviors which are formed or shaped or
altered by experience.   There are also important implications in this
distinction for evolution.

You  also seem not  to be familiar with the realities of the diversity
of animal behavior and ecology, nor with the range of reproductive and
developmental strategies used by different species nor with the
enormous scope of scientific work on these topics.  Hence your offhand
comment  about altricial vs. precocial development.  

Also, the relationship between DNA and the functioning nervous system
is not at all trivial.  Glib and simplistic statements of DNA
constructions underlying this or that (like the ability "to survive in
its mothers arms") don't really help advance  the discussion much.









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