Researchers with Embark Veterinary Inc., a dog DNA startup, genetically tested 6,070 dogs, linking that information with online surveys and photos submitted by dog owners who reported the observable characteristics of their animals.

After analyzing the data, researchers discovered the chromosome duplication near the ALX4 gene, which is important in the eye development of mammals, was strongly associated with the breed’s blue eye color. The variation is primarily observed in Siberian huskies, but it is also found in some Australian shepherds.

Although genomic tools are available for dogs for some traits, the genetic source of many characteristics has remained unknown. Two genetic variants were known to be the source of blue eyes in some dog breeds, but the variants did not explain the blue eyes in other dogs, such as Siberian huskies, researchers said.

The study is the first consumer genomics study conducted in animals and the largest genomics study ever conducted in dogs, researchers said.

Copyright 2017 U.S. News & World Report.