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From: colby@bu-bio.bu.edu (Chris Colby)
Newsgroups: sci.bio
Subject: Re: non-genetic evolution... not
Message-ID: <80392@bu.edu.bu.edu>
Date: 28 Apr 91 21:00:52 GMT
References: <79788@bu.edu.bu.edu> <47570@ut-emx.uucp> <79798@bu.edu.bu.edu> <18844@csli.Stanford.EDU>
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Reply-To: colby@bu-bio.UUCP (Chris Colby)
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In article <18844@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU (Chris Phoenix) writes:
>In article <79798@bu.edu.bu.edu> colby@bu-bio.UUCP (Chris Colby) writes:
>>	You are confusing the process of evolution with simple
>>change. If the gene pool of the wasps did not change (ie there
>>are still the same frequency of male and female determining 
>>genes), then the population did not evolve. This is true even
>>if there are more females than males compared to some time in
>>the past. 
>
>This is getting away from my question, but what do you consider the
>gene pool?
>If the bacteria mutated and this caused some change in the
>wasp, would you say the wasp had mutated?

	(Depending on what you mean by change) No, I would say the
environment (in this case an internal endosymbiont) caused a change
in the expression of the wasps genes.

>If you say "no", I have
>another question: would you say that we mutate if our mitochondria
>mutate? 

	Good analogy, in this case I would say yes. Why the difference?
Mitochondria and the rest of our cells are no longer autonomous; they
each depend on each other for survival. I would say that now the gene
pools count as one. In the wasp example, I don't know if the bacteria
could live without the wasp, but the converse is certainly true. For
that reason I would distinquish between the two gene pools.

>But the last theory I heard was that mitochondria used to be
>bacteria that our cells took in, once upon a time.  (Bill, I wrote
>this just before I got your mail.  I'll let it stand as a question to
>others, if they're interested.)

	Yes, this is the endosymbiotic theory. It is generally
accepted.

>Let me give an example to illustrate my point.
>>	Humans have been growing larger and heavier in recent
>>historical times. But this is not an evolutionary change; it
>>is a result of better nutrition and medicine.

>This is an extracellular change.  Obviously it is not a characteristic
>of the individual cells (ie if you pulled a cell out of Plato and a
>cell out of me and grew them in vitro you probably couldn't tell the
>difference in their offspring.)  I am not interested in this kind of
>change. 

>But I am interested in *intracellular* changes which do not involve
>the cell's nucleic acid, and preferably do not involve any nucleic
>acid.  Let me give you a hypothetical example that typefies what I am
>looking for: Suppose a cell has a structure of tubules.  These tubules
>serve as conveyors for various molecules, including some molecule
>necessary to build the tubules. 

	If you could get the tubules to grow in vitro supplying only
a nucleic acid free (or nucliec acid of random composition) cell
extract then I would say it counts as a genetic component. IE. it
contains the necessary info to replicate itself autonomously given
the appropriate environment. I would think this would be synonomous
with the mitochondrial example (mutual obligatory symbiosis).

>Should you distinguish between characteristics caused by expression of
>the genes and characteristics caused by the environment?  Your human
>size example is entirely dependent on the environment.

	Yes, one should distinguish between variation in a char-
actoristic due to environmental and genetic factors; this is key
to understanding evolution. In the human example, much of the variation
through time could be ascribed to environment, but not all. Two short
people are likely to have a short kid no matter how well you feed him/
her.

>Speaking of hormones, I've been following the discussion on hormonal
>control of fetal growth with interest.  But I haven't seen anyone
>address the question of where the hormones come from.  I think all of
>them will be coded for by the DNA of the original fertilized egg.

	Hormones are proteins coded for by genes.

>So a fertilized chicken-egg cell with dinosaur DNA will
>begin by producing dinosaur hormones.  If these hormones spread
>through the growing embryo in the same way (which is purely based on
>the embryo's environment and physical structure) then the cells will
>react to them just like dinosaur cells would.  So the embryo will keep
>developing like a dinosaur, and will become a dinosaur.

	The dinosaur DNA, however, would need the right cellular
environment to function (ie correct transcription factors to
activate the dinosaur genes, the appropriate equipment to pro-
cess dinosaur mRNA once transcribed (ribosomes and factors)). A
chicken cell may have diverged enough that it did not provide the
right environment. I don't know, experiment hasn't been done. 

>I hope this is still interesting for people...

	So do I.

Chris Colby
email: colby@bu-bio.bu.edu