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Humans, Chimps Almost a Match

Posted on: Thursday, 1 September 2005, 06:00 CDT

Humans and chimpanzees share an almost identical genetic inheritance, scientists report today in a landmark comparison that they call an "elegant confirmation" of Charles Darwin's theory of evolution.

Although scientists have long believed that humans and chimps are related, this comprehensive analysis of their separate genomes offers the best proof of their shared genetic past.

The 3 billion genetic letters in the two genetic blueprints are 96% identical with just 40 million differences, the researchers report in the journal Nature.

By delving more deeply into those differences, researchers hope to explain why humans are susceptible to certain diseases; why our evolutionary paths diverged from ancestral chimps 6 million years ago; and, on an even more basic level, what makes us human.

"We can peek into evolution's lab notebook and see what went on there," says Francis Collins, director of the National Human Genome Research Institute.

The analysis offers clues to the cause of diseases such as Alzheimer's and to why chimps and humans are susceptible to different diseases.

"Evolutionary analysis is a handmaiden to human medicine," says Eric Lander of the Broad Institute of the Massachusetts Institute of Technology and Harvard.

For example, in a discovery that could offer insights into Alzheimer's, researchers found mutations that turn off the human caspase-12 gene, which causes damaged cells to self-destruct. Those mutations weren't found in chimps, which aren't as susceptible to Alzheimer's. Knocking out caspase-12 in mice makes their brain cells more likely to survive with Alzheimer's-like damage.

Researchers also identified mutations in humans that were important for survival, including a gene associated with speech and a gene that ramps up response to sugar, an advantage in lean times but a potential ticket to diabetes today.

"Reading these two genomes side by side, it's amazing to see the evolutionary changes that are occurring," says Robert Waterston of the University of Washington. "I couldn't imagine Darwin looking for stronger confirmation of his theories."

Source: USA TODAY

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