Scientists Claim to Find Mechanism of Natural Selection

[Greg Claytor <gclaytor@flash.net>]

Dinosaur Listees,

I hope this isn't too off topic. I find this article interesting because
I've had SO many conversations with folks who think evolution and
existance of dinosaurs is false science.  They rail on me that carbon
dating is false, dinosaurs never existed, natural selection is baloney,
etc.

Greg


Reprinted from www.foxnews.com

Scientists Claim to Find
Mechanism of Natural Selection
2.00 p.m. ET (1900 GMT) November 25, 1998
By Amanda Onion


Nearly 140 years ago, a British naturalist published one of the most
controversial and influential studies in history. While Charles Darwin?s
The Origin of the Species was based largely on observation and theory,
scientists now claim they may have detected a tiny aspect of proof ? at
the cellular level ? of Darwin?s theory at work.

"Evolution used to be about arguments. Whoever had the best argument
won, because there was no way to study it," said David Gardiner, a
biologist at the University of California at Irvine. "This new study is
exciting because you can actually go in and see how changes happen."

Suzanne Rutherford and Susan Lindquist, of the Howard Hughes Medical
Institute at the University of Chicago, focused on the activity of
proteins ? substances known as the building blocks of life that are made
up of strings of amino acids. In their study, which appears in this
week?s edition of the journal Nature, Rutherford and Lindquist observed
fruit flies and the role of a specific protein, Hsp90, which exists in
nearly all creatures from bacteria to humans.

Hsp90 falls under a larger group of proteins known as "heat-shock"
proteins. More than 20 years ago, scientists discovered these proteins
are released when an animal is exposed to high temperatures or other
stresses such as reduced oxygen or chemical exposure. As other proteins
start to disassemble under the stress, the heat-shock proteins spring to
action and keep the other proteins in place. What makes Hsp90
interesting, however, is it also carries a second, separate role.

Under normal conditions, Hsp90 also acts as a "molecular chaperone" by
mediating the correct assembly of new proteins. By guiding the proteins,
Hsp90 ensures their processes lead to normal development of their
corresponding traits ? or their so-called expression ? in the body.
"Think about it as a piece of origami paper," explained Lindquist. "It
has to be folded just right for it to do what it?s going to do."

Having dual roles, the scientists found, can be overwhelming for Hsp90.
When a body falls under stress, Hsp90 attends to the crisis and can
start to neglect its normal role of ensuring the correct expression of
new proteins.

That?s when bizarre things begin to happen.

"We saw bristles sticking out instead of antennae, we saw eyes that were
crunched into all different kinds of shapes, we saw wings of all shapes,
stubby legs, we saw folded-over abdomens," Lindquist said about the
generations of fruit flies they raised after reducing levels of Hsp90.

These deformities, Lindquist argues, are evidence of natural selection
at work. If reducing the role of Hsp90 leads to the unmasking of
deformities, then, she infers, a wide array of variation must already
exist within each individual?s genetic code.

This variation surfaces when the body is under stress and gives rise to
quirks of nature ? an elongated nose or a sixth toe or a third eye ?
which either disappear from the species or persist if they prove
favorable to survival.

"The general impression among biologists has been that the genes that
control major pathways ? like for a leg or a wing ? are pretty much the
same," Lindquist said. "But this suggests there is a lot more variation
in the genome than we thought."

The question is, could Hsp90 act the same way in humans as it did in the
fruit flies? Could environmental hazards unleash a string of deformities
among humans, perhaps even leading to a different form of ourselves?

One clue may lie in another, more sensitive creature: the frog. Over the
past few decades, biologists have noted a marked decrease among frog
populations as well as a nearly 15-fold rise in the number of
deformities appearing in frog species. Scientists have traced the cause
to an increase of polluted waters but have been uncertain exactly how
the polluted waters affect the frogs.

According to David Gardiner, a biologist who specializes in frog
deformities, the problem does not appear to lie within the frogs?
genetic codes, but in agents responsible for gene expression, such as
Hsp90.

"What we?re seeing in the frogs is a developmental disruption," Gardiner
said. "I have a feeling there is a relationship between what?s happening
[to the frogs] and this study, but it?s unclear what the relationship
might be."

In their next work, Lindquist and Rutherford plan to explore that
question further and try to determine if Hsp90 or a similar protein
could be playing a role in the increasing number of deformities among
frogs.

Whatever answers the scientists find in the frog may carry implications
for our own biological future. The thin-skinned nature of the slippery
amphibian has earned it the distinction of being the "canary in the coal
mine" of impending environmental doom.

The scientists also hope their ongoing work may offer further evidence
to bolster the bearded naturalist Darwin's claims when he argued in 1859
that animals are constantly evolving.

"I think people tend to think that evolution happened and we?re done,
we?re it. And of course that?s not the case at all," said Gardiner.
"It?s an ongoing process. Through these studies we can see inside to the
nuts and bolts of the body and watch evolution take place."