Roan Zygosity Test

Roan is a white patterning coat color trait of intermixed white and colored hairs in the body while the head, lower legs, mane, and tail remain colored. Roan horses are born with the pattern, though it may not be obvious until the foal coat is shed. The white and colored hairs are evenly mixed in horses that inherit the classic Roan gene, which can differentiate this from several mimic patterns called roaning. Roaning patterns tend to be uneven in the distribution of white hairs, and the inheritance of roaning has not been defined. The Roan gene is found in a variety of breeds such as Quarter Horse, Paints, Peruvian Paso, Paso Fino, Welsh Pony, Miniature and Belgian, but not in Thoroughbreds or Arabians.

Although it has been suggested that Roan is a homozygous lethal, evidence from the Quarter Horse breed indicates otherwise. Production records have documented the existence of Roan Quarter Horses that produce 100% Roan foals. DNA tests have confirmed homozygosity in the genomic region that contains the Roan gene.

Note: Roan is inherited as a dominant gene but the specific mutation has not yet been identified, so there is no direct test for the gene. VGL has identified DNA markers in Quarter Horses and Paints associated with Roan that can be used to determine if a horse has the roan gene and how many copies. The following additional materials should be included to provide a complete analysis:

Materials Needed for Complete Analysis

• Hair sample from at least one parent
• Color photo of the subject horse, labeled with the horse’s name
• Three generation pedigree with color and patterns listed

This test is optional for all EBRA horses.

The Veterinary Genetics Laboratory (VGL) is a non-profit, self-supporting unit of the School of Veterinary Medicine at the University of California, Davis. We provide highly accurate genetic testing results and animal forensic services while also contributing to the educational and research mission of the school.

VGL provides animal parentage verification, identification, forensics services, genetic diagnostics, and genetic research for a broad range of domestic species as well as primates and wildlife species.