SAN FRANCISCO, Sept. 23 - Humans and chimpanzees may be genetically less similar than previously thought, according to a DNA comparison performed by a California Institute of Technology researcher.
Biologist Roy Britten said that human and chimp genomes are only 95 percent similar, a slight drop from the 98.5-percent similarity previously reported. Britten based his estimate on a computer program he wrote that compared approximately 780,000 base pairs of chimp and human DNA found in GenBank.
Getting a more accurate assessment of the genetic gulf between humans and chimps is an important first step in understanding how the species evolved, Britten said in a paper that appears today in the Proceedings of the National Academy of Sciences.
"A large number of these five-percent of variations are relatively unimportant," Britten said in a statement. "But what matters, according to everyone's idea, is regulation of the genes, which is controlled by the genes that are actually expressed. So to address this issue, you first have to know how different the genomes are, and second, where the differences are located."
Previous estimates relied on a method combining strands of a human and chimp DNA helix and using melting points to determine how many of the base pairs had bonded with each other, according to Britten. But this approach did not take into account insertion and deletion events, and thus gave incorrect estimates of the species' similarities.