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From: rs54@cunixf.cc.columbia.edu (Richard Sucgang)
Newsgroups: sci.bio
Subject: Re: Reconstructing cells from DNA
Message-ID: <1991Apr16.235422.20331@cunixf.cc.columbia.edu>
Date: 16 Apr 91 23:54:22 GMT
Organization: Columbia University
Lines: 31

In article <1991Apr14.211248.2072@alchemy.chem.utoronto.ca> mroussel@alchemy.chem.utoronto.ca (Marc Roussel) writes:
>In article <1991Apr13.203239.22379@hollie.rdg.dec.com>
>winalski@psw.enet.dec.com (Paul S. Winalski) writes:
>>I don't think that there are any cases of non-nucleic-acid-based hereditary
>>mechanisms in any known organisms.  Such mechanisms might be possible, but
>>living organisms don't make use of them.
>
>     I don't think that right, unless you want to extend the meaning of
>"hereditary mechanisms" to the point of meaninglessness.  Most
>biological morphogenesis in multi-celled organisms is now known to be
>the result of complex spatio-temporal interactions (chemical waves and the like)
>between embryo gene products and the chemical environment provided by
>the egg and/or uterus.  The number of digits that a person (or other 
>mammal) develops is now known to be determined by chemical waves at
>certain stages of development rather than by direct coding.  (I'm afraid
>that I can't produce any references at the moment due to a library
>strike at the University of Toronto.)
>
>				Marc R. Roussel
>                                mroussel@alchemy.chem.utoronto.ca

I take it you refer to the Turing models of pattern formation.
The problem is, what encodes for the source and sinks of the
gradient? This is still a genetic factor.  In drosophila, for example,
proper morphogenesis is dependent on how the maternal RNA is distributed
in the initial embryo.  That  remains quite essentially, genetic.

-rich
Richard Sucgang : Dept. of Anatomy and Cell Biology
Columbia University (sucgang@cuhhca.hhmi.columbia.edu; 
de slime god         rs54@cunixf.cc.columbia.edu)