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http://www.sciencedaily.com/releases/20 ... 081153.htm
Gene Duplication Adapts To Changing Environment
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Evolutionary theories assert that some of these duplicated genes may acquire new functions and take on new roles. But exactly how do these changes occur? And do they, as scientists suspect, really help organisms adapt to their environments?
New answers to these questions come from a study of leaf-eating monkeys by researchers at the University of Michigan, the National Institutes of Health, and the Chinese Academy of Sciences.
In the work, published online March 4 by Nature Genetics, U-M's Jianzhi Zhang and colleagues show how a duplicated copy of a gene encoding a pancreatic enzyme has evolved to help the monkeys cope with an unusual diet.
Zhang and colleagues were particularly interested in a pancreatic enzyme, RNASE1, which breaks down bacterial RNA. Most primates have one gene encoding the enzyme, but the researchers found that the douc langur, a colobine monkey from Asia, has two---one encodes RNASE1, and its duplicate encodes a new enzyme, which they dubbed RNASE1B.
The duplication occurred about 4 million years ago, after colobines split off from the other Old World monkeys, Zhang's analysis showed. Through a series of computations and experiments, the researchers determined that the original gene encoding RNASE1 remained unchanged after duplication, but its twin, which encodes RNASE1B, changed rapidly.
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Interestingly, the researchers found that the original enzyme works best at pH 7.4, but the new enzyme is most effective at pH 6.3---the acidity of the colobine small intestine. In fact, RNASE1B works six times better than RNASE1 under the more acidic conditions.
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"So now they have different jobs to do," says Zhang. "Before the duplication, you have one enzyme doing two jobs. After duplication, you have two enzymes, each doing just one job, but doing it better than the other."
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