Science  06 Jul 2012:
Vol. 337, Issue 6090, pp. 20

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  1. What Gets Yaks High?


    Nomads on the Tibetan plateau have relied on yaks instead of cows as their beasts of burden for the past 4000 years. Although the two are closely related—having diverged only 4.9 million years ago, around the same time that humans and chimpanzees parted ways—the domestic yak (Bos grunniens) is superbly adapted to the region's extreme elevations, which can exceed 4500 meters. Now researchers have uncovered the genetics behind this ability. The genome of a female domestic yak, reported on 1 July in Nature, reveals several genes that make it more suited for heights. Three genes help the animal regulate its body's response to hypoxia, or oxygen deprivation, at high-altitudes, and five genes help it optimize the energy it gets from its food, which is scarce on the plateau. Cattle lack these genes, which is why they cannot survive at the same heights as their bovine cousins. By understanding which genes are needed to live successfully at high elevations, the researchers say, scientists may be able to better treat and prevent altitude sickness and hypoxia-related complications such as high-altitude cerebral edema and high-altitude pulmonary edema, which can be fatal in humans.