Path: utzoo!censor!comspec!lethe!torsqnt!hybrid!scifi!bywater!uunet!tdatirv!sarima
From: sarima@tdatirv.UUCP (Stanley Friesen)
Newsgroups: sci.bio
Subject: Re: Sex and organelles (was: chloroplasts)
Message-ID: <98@tdatirv.UUCP>
Date: 24 Jan 91 21:18:48 GMT
References: <845@frc.frc.maf.govt.nz> <22722@well.sf.ca.us> <1179@ai.cs.utexas.edu>
Reply-To: sarima@tdatirv.UUCP (Stanley Friesen)
Organization: Teradata Corp., Irvine
Lines: 24

In article <1179@ai.cs.utexas.edu> throop@cs.utexas.edu (David Throop) writes:
>   The DNA in the organelles is separate from the DNA of the rest of
>the genome and each individual inherits all of its organelle DNA from
>just one parent.  As such, the the organelle DNA gets none of the
>advantages of sex.  ...
   
>    So if sex is so great why don't organelles have it?  Specifically,
>why has there not been evolutionary pressure to move the functions of
>the organelle out of the organelles' DNA onto the chromosomes?  Even
>if the organelles originated from symbiotes, why haven't the two
>genetic legacies been joined over evolutionary time?

The answer is that there has been such evolutionary pressure.  On the
assumption that the symbiotic hypothesis is correct, a great deal of the
original genome of the proto-organelle has been transfered to the nucleus.
What is left is almost (but not quite) vestigial.  The genes remaining in
the organelles mostly code for some (but not all) of the basic building
block of the organelle, but most of the regulatory and 'functional' genes
are in the nucleus. (For instance the genes coding for the energy transfer
chain that makes ATP are apparently nuclear).

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uunet!tdatirv!sarima				(Stanley Friesen)