"Study compares human and chimpanzee DNA" (2005)

SEATTLE, Aug. 31 (UPI) -- A study comparing humans and chimpanzee genomes has determined the cause of differences between the two species.

 Researchers found much of the genetic difference came about in events called segmental duplications, in which segments of genetic code are copied many times in the genome.

Lead researcher Evan Eichler, associate professor of genome sciences at the University of Washington-Seattle, and colleagues studied the chimp genome, looking for large-scale segmental duplications consisting of as many as 20,000 base pairs.

They found most of the genome change between chimps and humans can be attributed to large segmental duplications. Such large-scale genetic events altered more total base pairs -- about 2.7 percent of the genome -- than differences from single base-pair changes, which total about 1.2 percent of the genome.

"For all the talk of the 1.2 percent single base-pair difference and the importance of those, there's even more difference between the species due to duplication events," said Eichler. "Now we need to learn the role of those duplication events in species evolution and disease."

The study appears as a companion article to the draft sequence of the chimpanzee genome published in the journal Nature.