Zoos are the only places where white tigers exist: Treasured for their enigmatic coats, they've been hunted to extinction in the wild. Now, for the first time, scientists have found the DNA behind this snowy coat. Researchers analyzed the genomes of 16  related orange and white tigers in captivity, fully mapping those of the three parent tigers to show that a mutation in one pigment gene called SLC45A2 is at play—the very same gene that drives lighter coloring in people of European ancestry, chickens, and some mice. The team also found this SLC45A2 mutation in another 130 unrelated white and orange tigers, which helped confirm that in white cats it appears to silence red and yellow pigments but leave black untouched—hence the leftover stripes. The researchers are not yet sure how this happens; the mutated gene may alter the production of the pigment, melanin, they report online today in Current Biology. Some scientists had argued that white fur was a genetic defect intensified by inbreeding. But because the gene appears to affect only the cat's color, white tigers are simply genetically healthy variants of Bengal tigers, which, if bred carefully, might still survive well in the wild. Better captive breeding programs could improve their genetic diversity—perhaps spurring on the cat's eventual reintroduction into its native Indian forests.
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