Researchers comparing the human genome with the genomes of other species have discovered a surprising number of matching DNA sequences in a variety of vertebrate species, including the mouse, rat, dog, and chicken. The fact that these sequences have remained unchanged over long periods of evolutionary history indicates that they are biologically important, but for now their functions are largely a mystery. Published May 6 by Science Express (the online edition of the journal Science), these findings are the joint work of Gill Bejerano, a postdoctoral researcher at the University of California, Santa Cruz; David Haussler, professor of biomolecular engineering at UCSC and a Howard Hughes Medical Institute investigator; UCSC research scientist W. James Kent; and a team of researchers from the University of Queensland in Australia.By scanning the human, rat, and mouse genomes for matching regions of 200 or more DNA bases (As, Cs, Gs, and Ts), the researchers found 481 regions that were completely unchanged. All of the unchanged regions, referred to as “ultra-conserved elements,” were also found in the dog and chicken genomes, and two-thirds of them were found in the fish genome. But they could not be traced beyond the fish to nonvertebrate species whose genomes have been sequenced, such as the sea squirt, fly, and worm.
