EUGENE–Researchers at the University of Oregon have added new insights into the mysterious process of speciation–the mechanism by which new and genetically distinct species split off from a common ancestor, according to an article published in the Nov. 10 issue of Science magazine.

According to the article, genes are copied and duplicated in the process of DNA replication far more frequently–but also disappear from the genome far faster–than previously thought.

"We found a pretty astonishing set of results," says UO evolutionary biologist Michael Lynch, who co-authored of the article with UO computer scientist John Conery. "There is a lot of traffic going on–a lot more genetic coming and going than we used to believe occurred."

To get their results, Lynch and Conery sifted through vast amounts of genomic information searching for duplicate, or redundant, genes. The information databases they searched have resulted from the burst of genome research conducted in recent years. They studied genomes from species as varied as the mouse, chicken, nematode worm, rice plant, mustard plant (Arabidopsis thaliana), the zebrafish and human beings.

Once they identified the duplicate genes, the researchers carefully analyzed them. They were surprised to find that a typical genome has a few hundred to a few thousand duplications. Their analysis showed that duplications have about a one percent chance of arising per million years. This frequency, which is fairly constant among species they investigated, is high enough so that every gene would be duplicated in a few hundred million years.

"This tells us that there is an intrinsic property by which new copies of genes are arising and being inserted into the genome," Lynch says.

The vast majority of the duplicate genes, however, are short-lived in evolutionary terms, remaining in the genome only about two million to five million years. Of those that remain, most of the genetic duplications do not result in the species evolving new functions (novel phenotypes).

"But what is really exciting is that these duplicate genes may very likely be a leading mechanism of speciation," Lynch explains.

Simply put, if a gene duplicates within a species and subgroups of that species become isolated, the subgroups might each drop out a different redundant copy of the gene. The result could be that the species are no longer capable of interbreeding.

"What the data suggest is that if you are looking to find evidence of new species, you might want to look first at the genes that have been duplicated," he says. "These genes are very likely to be associated with where the species diverged."

Searching large genomic databases requires a great deal of computational power. Conery says that finding duplicates within a genome is something like looking for a word in an unalphabetized dictionary–except that in the case of gene databases the "words" are between 200 and 4,000 characters long.

"It took several months work, using our biggest computers, to complete this project," Conery says.

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