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Evolution? Can anyone really believe this? (fwd)

Richard Gordon gordonr at cc.UManitoba.CA
Fri Jun 30 11:29:41 EST 1995


Dear Steven,

You've made my point with your very discussion. You say we need both
genetic and epigenetic factors to explain embryogenesis, then describe in
detail only the genetic component. Either genetics controls epigenesis, or
epigenesis controls genetics, or both work together somehow (my
predilection), but in any case we need to get our act together and study
that epigenetic component. Genetics won't hack it alone. "Complete 
pathways" are not epigenesis, just complete genetics.
Best regards, -Dick Gordon, U.Manitoba[Jun29,95] 
On 26 Jun 1995, Steven Sullivan wrote:
> Richard Gordon (gordonr at cc.UManitoba.CA) wrote:
> : Dear Vernon,
> : This reply is a whitewash. We do not know how genes control any step of 
> : development, and the reverse may be true anyway. For nematodes, it is one 
> : thing to observe the cell divisions and differentiations, another to 
> : explain them. Sorry to be so blunt, Tom. The paradigm you give, though 
> : widely believed, lacks sufficient explanatory power.
> : Best regards, -Dick Gordon, U.Manitoba[Jun23,95]
> I'm not sure what you mean by this.  Care to elaborate?
> The reverse of 'genes control development' is 'development controls 
> genes'; I don't think any developmental biologist worth his or her salt 
> would deny that *both* of those are true, in the sense that genetic and 
> epigenetic factors shape the organism.  
> 
> Dev. biologists aren't just observing the fates of C. elegans cells,
> they're also 1) finding genes associated with developmental processes and
> 2) assessing their function.  Slowly, cascades of molecular signals are
> being identified.  It's hard work; there's a lot going on in even the
> 'simplest' cells.  But work in the fly is revealing that relatively few
> signals can set up the basic body plan.  What is lacking -- and this may
> be what you meant -- are complete pathways , particularly at the
> 'effector' end where genes that are switched on to give the specific
> phenotype of terminally differentiated cell shoudl reside.  But they're
> coming -- the work on MYoD and the muscle-cell differentiation pathways is
> particularly exciting. 



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