From: Chris Taylor (Christopher.Taylor@man.ac.uk)
Date: Mon 05 May 2003 - 16:09:59 GMT
There's a rather stark engineered example in Drosophila (fruit fly of
legend) called antennaepedia (near enough) where a homeobox (the BIG
developmental switchbox) mutation turns off the modifier program that
turns the foremost pair of legs into antennae, so you get a fly with
legs growing out of its head.
I'm struggling to think of the right example (the one you mean) but
here's another slightly tangential one: Trypanosomes (sleeping sickness
amongst other nasty diseases of humans and other species) cycle through
various (10ish maybe) clones over the lifetime of an infection, each
differing from its predecessors through mutation(s) that produce a
different glycoprotein coat (befuddling the immune's efforts to track it).
Then of course there's our old mate Biston betularia (beloved of A level
biology textbook writes everywhere) which went sooty (near cities) with
the rise of pollution as we industrialised, then reverted as the clean
air acts came along (although non-melanic forms were always there at a
low level so I suppose that doesn't count damn. Anyway I'm not wasting
all that typing. I'll think of one but it may take a little while...
Ray Recchia wrote:
> I'm reading "Darwin's Cathedral" by David Sloan Wilson and I have a
> general evolution question. Suppose a species initially evolves under
> circumstances where there is an advantage to having a drab grey color to
> provide circumstances. Then suppose circumstances change so that spot
> provide more of an advantage. Over time the species evolves an
> elaborate biochemical mechanism for spots that allows the species to
> survive effectively in this new environment. Next suppose the
> environment changes back so that drab grey is now more effective.
> Organisms can go back to drab without unevolving the entire mechanism
> for spots. Instead they can just have point mutations that disable the
> spots. Then if the environment changes again so that spots are better,
> instead of re-evolving the whole spot system again, all that is
> necessary is that a few individuals lose the point mutations preventing
> spots from being expressed. This means that spots can reappear much
> more quickly the second time than they did the first time.
> So my question is, are there any real examples of this occurring in
> nature? Is there a term that is used to describe this phenomenon?
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> Journal of Memetics - Evolutionary Models of Information Transmission
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-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Chris Taylor (email@example.com) http://bioinf.man.ac.uk/ »people»chris ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ =============================================================== This was distributed via the memetics list associated with the Journal of Memetics - Evolutionary Models of Information Transmission For information about the journal and the list (e.g. unsubscribing) see: http://www.cpm.mmu.ac.uk/jom-emit
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