Of Mice and Mammoths ; Details of a Species' DNA Can Shed Light on Evolutionary Adaptation

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To learn how an extinct mammoth managed its hair color, just ask a mouse. A simple mutation in a single gene enables some beach mice to adopt hair-color patterns that blend in with the sand. DNA from a bone of a 43,000-year-old Siberian woolly mammoth shows the same mutation. This fact implies that mammoths and mice used the same genetic mechanisms to color their hair to fit their lifestyles.

This news from genetic explorers, reported last Friday in Science, illustrates how details of a species' DNA can shed light on evolutionary adaptation. If those explorers can get enough of the stuff from extinct species, it would also give us a more accurate look back in time.

Holger Rmpler at the University of Leipzig in Germany and colleagues, who studied the mammoth bone, warn against making too much of their discovery. They note that "it is currently impossible" to know the adaptive value of hair color for mammoths. But their work does show that scientists can discover the function of ancient genes.

"This opens up the possibility of studying a wide range of extinct species' features invisible in the fossil record," they say.

The gene in question provides codes for a protein that is a key factor in determining hair color in animals, including humans. Like all proteins, it consists of subunits made from amino acids. Hopi Hoekstra at the University of California at San Diego and colleagues show how a small change in just one of these subunits correlates with hair-color change in beach mice that live on Florida's barrier islands. Mice that live on light sand are lighter colored than their mainland cousins.

Geneticists have known that changes in how genes are regulated account for many differences between organisms. …


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