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