Boleh dibilang tiap hari para ilmuwan diseluruh dunia memperbaiki dan 
menyempurnakan teori Darwin..

Dazn masih saja ada manusia dungu kayak anjing yang masih percaya kepada omong 
kosong dan kibulan Bible dan al--Mushaf yang bilagn Tuhan menicipatakan 
manausia dari tanah liat...

Lha nggak ada bukti kok bahwa Tuhan atau Allah seperti yang diriwayatkan Bible 
atau al-Mushaf itu memang ada.

Yang ada cuma omong kosong dan, kibulan.doang

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   Web address:
     http://www.sciencedaily.com/releases/2009/02/
     090205142134.htm     
Rapidly Evolving Gene Contributes To Origin Of Species
enlarge

Drosophila (fruit flies). Certain genes in the fruitfly's own genome serve 
little purpose other than to replicate themselves. (Credit: iStockphoto/Tomasz 
Zachariasz)

ScienceDaily (Feb. 7, 2009) — A gene that helped one species split into two 
species shows evidence of adapting much faster than other genes in the genome, 
raising questions about what is driving its rapid evolution.

The paper in the Feb 5 issue of Science shows that the gene has connections to 
another previously identified "speciation gene." Both genes code for key 
proteins that control molecular traffic into and out of a cell's nucleus. The 
researchers believe an arms race of sorts inside the cell drives these genes to 
evolve rapidly—and as a consequence makes closely related species genetically 
incompatible with one another.

"When we cross two species of fruit fly, which had split from one another 3 
million years ago, some of the hybrid offspring die," says Daven Presgraves, 
professor of biology at the University of Rochester and Grass Fellow at the 
Radcliffe Institute for Advanced Study at Harvard University. "This tells us 
that genes from one species are no longer compatible with genes from the other 
species. We've now found that a functionally related group of genes is 
responsible, with different versions of the genes having evolved in the two 
species. And just as Darwin predicted 150 years ago, they evolved by natural 
selection."

Presgraves has some ideas why two of the genes in particular, called Nup160 and 
Nup96, have evolved so quickly: they act as gatekeepers of a cell's nucleus, a 
favorite target for viruses and even malicious genes within the fly's own 
genome. Presgraves says that these genes probably experience constant assault 
and thus must constantly adapt. That these genes also prevent genetic mixing 
between closely related species is incidental—the origin of new species is just 
a by-product of evolutionary arms races, he says.

When two populations become separated by a geographic barrier—a mountain range 
or an ocean—they evolve independently. Presgraves and his graduate student 
Shanwu Tang studied a fruit fly species from Madagascar that long ago become 
separated from its sister species in Africa. Separated by an expanse of the 
Indian Ocean, the two independently evolving species accumulated genetic 
differences. Tang and Presgraves's unexpected finding, however, was that in 
both species, the Nup160 and Nup96 genes became so different so quickly that 
they are no longer compatible.

"When the same genes in two different species evolve quickly, they become so 
different that they can be incompatible," says Tang. "The genes from one 
species can't talk to the genes in the other species any more."

Six years ago, Presgraves found that the Nup96 gene kills hybrid offspring 
between these fruitfly species. Since, two species can be separated by any 
number of incompatible genes with different functions, he and Tang were 
surprised when they found that Nup160 also kills hybrid offspring. Both genes 
encode parts of the same gatekeeping complex that regulates what gets in or out 
of a cell's nucleus.

"Shanwu and I were shocked," says Presgraves. "Only half a dozen such 
'speciation genes' are known, so to find two of them that interact with one 
another as part of the same complex says that multiple parts of the same 
complex have evolved."

Presgraves and Tang are now investigating other genes that cause hybrid 
lethality, as well as trying to discern why natural selection has caused this 
particular complex to evolve so quickly. Presgraves has said viruses could be 
responsible for the rapid evolution of the complex because viruses act by 
inserting their own DNA into a host cell's, which means getting their DNA 
through the gatekeeper complex. In a molecular arms race, the viruses 
constantly adapt to sneak through the gates, and the gatekeepers adapt to 
thwart the viruses.

Presgraves even suggests another, more exotic arms race. Certain genes in the 
fruitfly's own genome serve little purpose other than to replicate themselves. 
These selfish genes can also manipulate the gates for their own needs, 
requiring the gatekeepers to adapt to keep the selfish genes under control.

As a 2008-2009 Radcliffe fellow, Presgraves is focusing on the special role of 
sex chromosomes in speciation. He is combining genetic mapping and comparative 
genomics approaches to determine why the X chromosome is a hot spot for 
speciation genes in two closely related species of Drosophila fruit flies.
Adapted from materials provided by University of Rochester, via EurekAlert!, a 
service of AAAS.
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following formats:
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MLA
University of Rochester (2009, February 7). Rapidly Evolving Gene Contributes 
To Origin Of Species. ScienceDaily. Retrieved February 8, 2009, from 
http://www.sciencedaily.com­ /releases/2009/02/090205142134.htm


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