- (AP) -- If the world suddenly gets hotter,
you might survive better with a new skin color, or you might sprout a
tail to maneuver in the dense tropical forest that spreads around the
globe.
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- And, if scientists are correct, you might
already be carrying the genes for these radical traits, and more.
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- Scientists working with fruit flies believe
they have unlocked a vault of last-ditch genetic variations that kick
in to help organisms survive in a much altered form that defies the neatly
predictable, incremental pace of evolution.
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- Researchers at the University of Chicago
and the Howard Hughes Medical Institute report in Thursday's issue of
the journal Nature that the fruit flies expressed these prefabricated
variations -- from weird limbs to different wings -- when scientists fooled
the insects into thinking their climate was changing.
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- The physical changes erupted in the span
of a few generations in the face of supposedly new and dire living conditions.
In doing so, they radically changed the appearance and behavior of a
creature that had looked and lived the same for eons.
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- Doomsday Genes Well Hidden
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- Researchers caution this cache of doomsday
genes has been unlocked only in controlled experiments.
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- Such emergency countermeasures are kept
under tight molecular wraps in normal circumstances, they said. Nor has
it been determined if these genes actually work this way in nature.
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- "This sounds like a very bad thing,
and no doubt it is for most of the individuals," said study co-author
Susan Lindquist of the University of Chicago. "But for some, the
changes might be beneficial for adapting to a new environment. Genetic
changes exposed in this way become the fodder for evolution."
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- In the 19th century, Charles Darwin described
evolution as a gradual, orderly march by a species toward self-improvement.
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- In the fossil record, most evolutionary
changes are seen to have unfolded over millions of years. But not always.
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- Punctuated Equilibrium Theory
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- The theory of punctuated equilibrium
championed by paleontologist Stephen Jay Gould and others suggests that
evolution is a messy business driven by random disasters that force survivors
to adapt hurriedly to new environmental conditions.
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- For example, mammals and other life forms
flourished after an asteroid or comet hit Earth 65 million years ago, but
dinosaurs perished.
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- "Evolution is often thought of as
incremental," said biologist Andrew Cossins of the University of
Liverpool in England. "But the fossil record contains many examples
of apparently rapid changes in body form. This mechanism provides, for
the first time, a means by which changes in body form can be substantial
and stepwise rather than progressive."
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- Other scientists want to see whether
such drastic variations can occur quickly outside the laboratory.
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- "In real life, are there organisms
that change this way? Are there examples in nature that are going begging
for an explanation like this?" said Aaron Bauer, a lizard geneticist
at Villanova University.
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- Bauer studies a group of geckos native
to the deserts of southwest Africa. He said one type of lizard could be
a candidate for study because it looks and acts differently, yet its
genome is nearly identical to other lizards in the area.
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- "If this molecular mechanism could
be shown to be generally applicable among different organisms, it would
be an important advance," Bauer said.
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- In the fruit fly experiments, the Chicago
researchers determined that the genetic variations held in reserve depended
on a protein called Heat shock protein 90.
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- Hsp90 is known as a chaperone protein.
As temperatures rise, it prevents other proteins from going awry and disrupting
normal cell functions and growth, and also prevents degenerative diseases.
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- However, Hsp90 gets spread too thin when
conditions continue to deteriorate. With the chaperone distracted, many
different proteins begin to misfire in cells. Genetic variations that
were held in reserve begin to trigger.
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- In the experiments, the researchers deliberately
reduced the levels of Hsp90 in fruit flies to simulate the biological
response in fruit flies to climate change.
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- As many as 90 percent of the flies' offspring
emerged with oddly shaped wings, strange bristle configurations and limb
deformities. The eventual evolutionary benefits of these genetic changes
were unknown, the researchers said.
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- The abnormalities persisted even when
Hsp90 levels were returned to normal in later generations, suggesting
the changes had become permanent in the fruit flies' genetic code, Lindquist
said.
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- http://www.cnn.com/TECH/science/9811/25/sudden.evolution.ap/
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