Roan Zygosity TestQuick Summary
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Phenotype: Roan is a white patterning coat color trait characterized by intermixed white and colored hairs in the body while the head, lower legs, mane, and tail remain colored.
Mode of Inheritance: Autosomal dominant
Alleles: N = Normal, Rn = Classic Roan
Breeds appropriate for testing: Many breeds
Explanation of Results:
- Horses with N/N genotype will not have the classic roan pattern and cannot transmit this roan variant to their offspring.
- Horses with N/Rn genotype will have the classic roan pattern. They may transmit this roan variant to 50% of their offspring. Matings with N/N genotype will result in a 50% chance of producing a roan foal.
- Horses with Rn/Rn genotype will have the classic roan pattern. They will transmit this roan variant to all of their offspring. Matings with any genotype are predicted to produce all roan offspring.
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 Helpful for a Complete Analysis (strongly recommended but not required)
- 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
Species
Breed
| Test Result | Classic Roan |
|---|---|
| N/N | No copies of classic roan detected. |
| N/Rn | 1 copy of classic roan detected. Horse will have the classic roan pattern. |
| Rn/Rn | 2 copies of classic roan detected. Horse will have the classic roan pattern. |
Sponenberg, D. P., Harper, H. T., & Harpar, A. L. (1984). Direct evidence for linkage of roan and extension loci in Belgian horses. Journal of Heredity, 75(5), 413-414. doi: 10.1093/oxfordjournals.jhered.a109968
Marklund, S., Moller, M., Sandberg, K., & Andersson, L. (1999). Close association between sequence polymorphism in the KIT gene and the roan coat color in horses. Mammalian Genome, 10(3), 283-288. doi: 10.1007/s003359900987
