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From: cphoenix@csli.Stanford.EDU (Chris Phoenix)
Newsgroups: sci.bio
Subject: Reconstructing cells from DNA
Message-ID: <18637@csli.Stanford.EDU>
Date: 11 Apr 91 05:41:38 GMT
Organization: Center for the Study of Language and Information, Stanford U.
Lines: 26

I recently started speculating about non-genetic mutations in cells, as a 
result of speculating about non-software mutations in self-replicating 
machines.  This led to wondering whether it is really possible to reconstruct
a cell from only its DNA.
I'm sure everyone's read about recreating dinosaurs by finding dinosaur DNA 
in tar pits or ice and injecting it into a chicken embryo (or something like
that).  My question is whether DNA really completely determines what a cell
"grows up" to be.  
I recently heard of an experiment in which a paramecium (I think) had part of
its cell membrane removed, rotated, and put back, so that some of the spines
were backwards.  Its "descendants" also had backwards spines.  This implies
the possibility of one DNA set (sorry, I forget the fancy word) being 
consistent with several different cells.   This would mean that:
1) Dinosaurs could not be replicated from their DNA alone, since there might
be differences between dinosaur cells and host cells that the dinosaur DNA 
could not fix.
2) Evolution of cells might take place by other mechanisms than just
mutation of DNA.  Non-genetic changes in cells might be hereditary.
In the case of sexual reproduction, I would expect that such changes
would be passed on only through the mother.
Is this totally off base, or is non-genetic evolution a possibility?
(Yes, I know mitochondria have their own DNA, and they evolve (or at 
least mutate.  I'm more interested, though, in changes to the cell
that do not involve any change in nucleic acid.)

Chris Phoenix		cphoenix@csli.stanford.edu