Breeds: Any

Samples Accepted: Blood, Hair

Locus: D locus

Color: Dun causes a lightening of a horse’s base color.  It is dominant, so only one copy of the mutation is necessary to be able to see the color.  In addition to diluting the base color, the dun variant causes what are known as “primitive markings”.  These include a dark stripe of hair going down the middle of the back (dorsal stripe), dark stripes on the legs, and occasionally a dark area of hair going over the shoulders.

Genetic studies have revealed that dun was the color of all original horses, what is generally called the “wildtype”.  The non-dun colors so common today are actually the “mutations” caused by two different variants, designated non-dun 1 and non-dun 2.

Dun: The horse will have a diluted base coat color and primitive markings.

Non-dun 1: The horse will have a normal base coat color, but may also show primitive markings.

Non-dun 2: The horse will have a normal base coat color and no primitive markings.

A horse may have a combination of any two of these variants.

The possible genotypes are:
D/D            The horse will be dun in color, and will pass the dun variant to all of its offspring

D/nd1        The horse will be dun in color, and will pass the dun variant to 50% of its offspring.  It will also pass the non-dun 1 variant to 50% of its offspring.

D/nd2       The horse will be dun in color, and will pass the dun variant to 50% of its offspring.  It will also pass the non-dun 2 variant to 50% of its offspring.

nd1/nd1    The horse will have a base coat color of normal intensity (undiluted), but will also likely have primitive markings, including a dorsal stripe and leg stripes.  The horse will pass the non-dun  1 variant to 100% of its offspring.

nd1/nd2    The horse will have a base coat color of normal intensity (undiluted), and may have primitive markings, including a dorsal stripe and leg stripes. It will pass the non-dun 1 variant to 50% of its offspring, and the non-dun 2 variant to 50% of its offspring.

nd2/nd2     The horse will have a base coat of normal intensity (undiluted) and will have no primitive markings.  It will pass the non-dun 2 variant to 100% of its offspring.

Test Information: This mutation test identifies three variants:

D:  the original “wildtype” sequence that results in the Dun coloration

non-dun 1: a single nucleotide change close to the TBX3 gene

non-dun 2: a 1.6 kb deletion mutation close to the TBX3 gene

Imsland, F., McGowan, K., Rubin, C.J., Henegar, C., Sundström, E., Berglund, J., Schwochow, D., Gustafson, U., Imsland, P., Lindblad-Toh, K., Lindgren, G., Mikko, S., Millon, L., Wade, C., Schubert, M., Orlando, L., Penedo, M.C., Barsh, G.S., Andersson, L. :     Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses. Nat Genet :, 2015. Pubmed reference: 26691985. DOI: 10.1038/ng.3475.

Further information is available at the Online Mendelian Inheritance in Animals website.

Test #: H219
Cost: 35 € (excl. VAT)
Time: 7-10 Days