Fossil genetics

Tony Long tdlong at ucdavis.edu
Sat May 7 13:04:54 EST 1994

In article <wgallin.1118714328C at NEWS.SRV.UALBERTA.CA>,
wgallin at gpu.srv.ualberta.ca (Warren Gallin) wrote:
> an early biological determinant of mating incompatibility is probably
> changes in chromosome structure, which will interfere with functional
> meiosis.  To see that, you would need a full karyotype analysis;  I think
> that is extremely unlikely.  Most of the structural genes are not going to
> confer mating incompatibility.

	What is your evidence for this?  Sure there are a lot of karyotype
differences between species, but such changes do not imply they are the
cause of reproductive isolation.  I suggest looking at recent work out of
the Wu lab at University of Chicago (or any of the other labs doing work in
this area) on reproductive isolation between species in the Drosophila
group.  This work suggests that a number of 'factors' are associated with
reproductive isolation in these groups.  As these factors are not cloned
(not yet anyway) it is not clear if they represent structural or regulatory
genes.  Eitherway, at least in Drosphila, there is evidence that
reproductive isolation can evolve before karyotype changes.  Mileage may
vary in other taxa.

> you're suggesting, but I think it is in the realm of science fiction right now.
> Warren Gallin,
> Department of Zoology, University of Alberta
> wgallin at gpu.srv.ualberta.ca

	Even if one had the sequence of the entire genome of an extinct species,
the task of associating this variation with ANY phenotypic differences (be
it isolation or nose size) between species would remain in the realm of
science fiction.  In order to map such loci one needs to associate DNA
variation with phenotypic variation in the F2 (or a subsequent backcross)
generation of a cross between the species.  Of course in order to do this
we would have to recreate the species in a Jurassic Park fashion ... or
make transgenic animals that differ only in a candidate gene (this is
possible in Drosophila).  

Tony Long
Center for Population Biology
U. C. Davis
Davis, CA
tdlong at ucdavis.edu

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