Elegant and expressive, blue-eyed dogs have some of the most unforgettable furry faces around. Scientists have thrown dog-lovers a bone: clues as to what causes this eye-catching trait.

Scientists know that blue eyes are related to the coat color of some dogs, like merle (or splotchy-coated) Australian shepherds. But what about other dogs that sometimes have piercing baby blues, like the striking and popular Siberian husky? (Related: What Makes a Great Sled Dog? Breed, Ambition, Tough Feet.)

Scientists at a DNA testing startup set out to explore the question by looking into other variations—besides coat color—that might cause blue eye color in dogs.

In the largest study ever to compare dogs’ complete genetic profiles, researchers found a genetic tweak that can