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Thursday, April 10, 2008

Experimenters Make Evolution Chip

Scientists have created a "Darwin chip" that can show students the process of evolution by natural selection in real-time. Researchers at The Scripps Research Institute in La Jolla, California, made the chip-based evolution system by dropping an RNA molecule called a "ligase" into a pool of other RNA molecules, where it would sew another RNA strand to itself and then duplicate. (Because of errors in copying, duplication isn't always perfect, which means sometimes the new ligases are better sewers, sometimes worse.) "A population of billions of RNA enzymes with RNA ligase activity was made to evolve continuously, with real-time monitoring of the population size and fitness. Whenever the population size reached a predetermined threshold, chip-based operations were executed to isolate a fraction of the population and mix it with a fresh supply of reagents," study authors Dr. Gerald Joyce, a molecular biologist and chemist, and Brian Paegal, a researcher in Joyce's lab, write in PloS Biology. "These steps repeated automatically as the population adapted to the imposed selection constraints within a period of several hours." After only 70 hours of duplications, the chip produced ligase molecules that were 90 times more efficient at finding and stitching other RNA molecules to itself. Joyce—who calls this "survival of the fittest on the smallest scale possible"—believes the quick, tangible results might help convince those who still doubt Darwin's theory of evolution. "This is evolution of molecules as a fact, not a theory," he said in a press release.
"No one has been able to observe what the process looks like until now," Paegel added. "It's like before you could only see little bits of a fine painting. Now, we can step back and watch a complete picture of evolution happening at its most fundamental level, on a molecular scale." And it's not an expensive or terribly hard picture to re-create; making the chip costs only about eight dollars. —Evan Peck.