Re: Darwin, Evolution, the Animal Kingdom, and Man

From: John Hasenkam (johnh_at_faraway.)
Date: 12/07/04 

Date: Tue, 7 Dec 2004 18:27:00 +1000

"Michael Olea" <oleaj@sbcglobal.net> wrote in message
news:BDD92B72.CCB3%oleaj@sbcglobal.net...
> in article oJ%rd.27156$kI6.1506597@news20.bellglobal.com, Wolf Kirchmeir
at
> wwolfkir@sympatico.ca wrote on 12/3/04 7:37 AM:
>
> > Lester Zick wrote:
> > [...]
> >>
> >> I find myself wondering if there are any biological evolutionary
> >> mechanisms other than random mutation mechanisms of natural selection?
>
> >>
> >> Regards - Lester
> >
> >
> > Don't wonder, read. You'd find out, eg, that the expression of genes
> > depends on the organisms' environment, which means that inactive "legacy
> > genes" may become active when the environment changes. ...

There has been some interesting research touching on this. Heat Shock
Protein 90, released under cell stress, seems to potentiate changes in gene
transcription. Interestingly, research published last week showed that plain
old environmental stress can age cells by 10 years. This makes sense because
when cortisol saturates GRs, the protective gene response tends to be
diminished(AP 1 set, driven by NFkB, is inhibited because GR and NFkB
transcription are mutually exclusive, sort of; that's the notion anyway).
HSP 90 is tied to the GR and is released once the cortisol binds to this
receptor. Thus, under stress, not only are protective processes inhibited
but also hsp90 *may* be driving differential gene expression. I wonder if
this has any relation to Wolf's earlier comments about the rapid return to
the wild type of domesticated animals. So then, altered gene expression and
stressful environments do impact on the genome. Not specific though but nor
is it strictly chance mutations. Note also that hsp90 enables some cancer
cells to fight off toxins and hsp90, as with many hsps, is released under
cell stress conditions.

Note: a little stress goes a long way. With a little stress only MR
occupation occurs and this generates a protective response.

Remember: Even Darwin noted that natural selection is not the sole
determinant.

Also: doubtful this one but is causing a bit of a stir. Some Australian
scientists have claimed that changes in immune genes can occur vertically in
a Lamarckian fashion. They claim these changes arise because immune
processes do penetrate the Weissman Barrier (that which purportedly protects
gametes from external influence). The book is called Lamarck's Signature.
Haven't read it but I do find the idea interesting because some changes in
immune related genes do appear to be rather rapid.

Couldn't find the ref I had in mind re hsp 90(brains still work better than
databases!) but found this

Journal of Animal Breeding and Genetics
Volume 117 Issue 4 Page 275 - August 2000
doi:10.1046/j.1439-0388.2000.00254.x

Exploitable genetic variation can be changed under environmental and genetic
stress. Consequences for livestock breeding a review
H. Kräußlich
Summary

Livestock breeding is exploitation of genetic variation in herdbook
populations. Results of long term selection (domestication) experiments led
to the assumption that some genes are normally silent and can be activated
under genetic and environmental stress. Rutherford and Lindquist (Nature
336: 336342, 1998) provided the first evidence of a molecular mechanism
which can activate silent genes. This article discusses this field of
research with respect to the livestock breeding.

If you Google this string you will see lots of interesting refs

"hsp 90" genome variation

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