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Plants Fix Genes With Copies From Ancestors

Pruitt said others have occasionally noted the appearance of "revertant" plants but ignored them, assuming they were the result of sloppy technique or other errors. By contrast, Pruitt and Lolle took the observation seriously, said Elliot Meyerowitz, a pioneering arabidopsis researcher at California Institute of Technology.

"There are different sorts of scientists. Some like to ignore the exceptions, and others like to concentrate on them," Meyerowitz said, adding that he suspects the novel gene-fixing mechanism is present in a wide variety of organisms, including animals. He suspects the trick has been overlooked because it operates only some of the time and because scientists have been predisposed to write off the evidence as random events.

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The discovery, he said, seems on par with a few others that have significantly modified scientists' understanding of genetics since Mendel. Studies in corn led to the discovery of an important gene-shuffling mechanism that has since been found in other plants and animals, including people. Studies in insects found a new mechanism for gene regulation that has since been found throughout the biological world. And a mechanism for turning off genes, first identified in soil-dwelling roundworms and since found in humans, too, is now one of the hottest topics in medical genetics because of its potential to shut down disease-causing genes.

"I won't be surprised," Meyerowitz said, if the new DNA editing mechanism is present in people, too.

Gerald Fink, a professor of genetics at the Whitehead Institute for Biomedical Research in Cambridge, Mass., said it would be important to identify exactly how the mechanism operates and whether it works in all kinds of genes. But he said he was convinced that "something weird is definitely going on." The work serves as a good reminder, he added, that the central genetic code by itself is only part of the mystery of how inheritance works.

"This gives the lie to the idea that you know everything once you sequence the genome. You don't."

Lolle said the trick is probably a lifesaver for plants, which cannot run away from radiation, environmental extremes and other insults to their DNA. It is probably especially important for self-pollinating plants such as arabidopsis, she said, which are constantly at risk of becoming seriously mutated as a result of inbreeding.

She described the mechanism as one that allows a plant to reach back in time for a version of a gene "that's already been road-tested."

Lolle said she foresees medical benefits as scientists learn to control the molecular counterpart she suspects is in humans.

"I'm very optimistic," she said. "Once the scientific community takes hold of this, it's going to work forward at a very rapid pace."

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