In a study published in the July 22 issue of the journal Science, a team of 25 scientists from the United States, France and Singapore compared the organization of the chromosomes of eight mammalian species: human, mouse, rat, cow, pig, dog, cat and horse. Using sophisticated computer software to align and compare the mammals' genetic material, or genomes, the team determined that chromosomes tend to break in the same places as species evolve, resulting in rearrangements of their DNA. Prior to the discovery of these breakage hotspots, the prevailing view among scientists was that such rearrangements occurred at random locations.
"This study shows the tremendous power of using multi-species genome comparisons to understand evolutionary processes, including those with potential relevance to human disease," said NHGRI Scientific Director Eric D. Green, M.D., Ph.D. "The dog genome map generated by NHGRI researchers and their collaborators played a key role in these new analyses. Furthermore, the team took full advantage of the wealth of human, mouse and rat genome sequence data generated by the recently completed Human Genome Project."
Chromosomes are the threadlike "packages" of DNA located in the nucleus of each cell. When cells divide, a chromosome occasionally breaks and the fragment can get stuck onto another chromosome. In addition, fragments may break off from two different chromosomes and swap places.
Chromosomal breakages, also referred to as translocations, are thought to be important in terms of evolution. When chromosomes break in egg or sperm c
Contact: Leslie Saint-Julien
NIH/National Human Genome Research Institute