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From: jda@brunix (Jeff Achter)
Newsgroups: sci.bio
Subject: Re: Creating life
Keywords: Life
Message-ID: <19690@brunix.UUCP>
Date: 2 Nov 89 22:55:57 GMT
References: <2461@umbc3.UMBC.EDU> <4516@utastro.UUCP> <2189@hudson.acc.virginia.edu>
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Reply-To: jda@cslab9a.UUCP (Jeff Achter)
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Organization: Brown University Department of Computer Science
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Since DNA determines protein, and protein determines enzyme function,
and enzyme function is basically life, theoretically we should be able
to craft an organism from scratch.  Unfortunately, there are enough
holes in our knowledge that this is impractical.  Some of the problems
include: 

	Gene expression and transcription.  A large part of a DNA
strand is junk--nucleotides which are never expressed as amino acid
sequences.  Additionally, we don't know how the transcription enzymes
know when to start and stop transcribing a stretch of DNA.  There are
three possible reading frames on each of the two complementary
strands; which will be expressed?  Until we know this, we can't
reliably craft a genome.

	Protein structure.  This is a biggy.  The function of a
protein is determined by its three dimensional structure.  While
progress is being made in biophysics, the models aren't good enough to
predict the tertiary and quaternary structure of a protein, given its
primary structure (the sequence of amino acids).  Thus, it is very
difficult to craft proteins with desired functions.

	Putting everything together.  Remember, there are *lots* of
different proteins in even the simplest cell.  If we build an organism
from the bottom up, we have to account for all the different functions
a cell needs for survival--transcription, membrane building,
energetics catalysis, etc.  It would be far easier to build a virus,
but... are viruses alive? :-)

In short, we're working on it, but not yet.



  Jeff Achter        |  PO Box 1320           | 
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