Two bioinformatics researchers from the University of California at San Diego have pulled the rug out from under a central tenet of evolution—that mutations appear at random in different parts of our DNA. Pavel Pevzner and Glenn Tesler compared the just-sequenced mouse genome with its human counterpart and analyzed where rearrangements, a common type of genetic mutation, occur. This work, which highlights how the two species have diverged over millions of years, shows unexpected zones of stability and change.
Pevzner likens the genome of the common ancestor of mice and men to a deck of cards. If you have two identical decks and shuffle each blindly, you would expect to see two independent patterns of cards. “Now suppose the seven, eight, and nine of spades always stay together, but there’s always a break between the nine and the ten-that’s what we’re finding,” Pevzner says. The vast majority of the genetic rearrangements he has found occur in about 300 regions that make up less than 5 percent of the total genome. “It’s like having earthquake fault lines running through your DNA.”
The discovery may force biologists to reevaluate how they define species and how they infer evolutionary relationships. It could also serve as a diagnostic tool for cancer. Most forms of cancer resemble evolution happening on an accelerated timescale, with a sudden explosion of genetic rearrangements taking place in the cells. A gene map of the pattern of rearrangements could allow doctors to measure more precisely how far a cancer has progressed. “It would be a good way to get a really practical device out of the published genome,” Pevzner says.