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From: tmb@talcott.UUCP (Thomas M. Breuel)
Newsgroups: net.bio
Subject: Re: Morphological Asymmetry
Message-ID: <513@talcott.UUCP>
Date: Sun, 22-Sep-85 11:59:20 EDT
Article-I.D.: talcott.513
Posted: Sun Sep 22 11:59:20 1985
Date-Received: Wed, 25-Sep-85 09:49:51 EDT
References: <295@ihnet.UUCP> <772@nmtvax.UUCP>
Distribution: net
Organization: Harvard University
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In article <772@nmtvax.UUCP>, shipman@nmtvax.UUCP writes:
> A more general question: how do cells in the embryo know "where
> they are" on the body plan?  How does a cell know it's going to
> be part of a big toe and not an eyelid?  I've been trying to
> find someone who will venture an answer to this one for years.

Yes. That is what developmental biology is all about.
Developmental biologists have been trying to *find*
an answer to this one for more than a century.

Seriously, though: there is probably no magic going on.
Positional information may given by chemical gradients, by 
electric fields and by cell surface interactions.

But these are only the physical means by which a mechanism
of pattern formation and morphogenesis can be implemented.
There have also been many suggestions as to the nature
of the mechanism itself. They all await experimental
verification.

					Thomas.


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