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Locus Information: D locus

Inheritance: autosomal dominant

→ Horses with one or two copies of this variant (D/nd or D/D) show the diluted coat color and the primitive markings (zebra stripes, dorsal stripe) on their legs and back. Horses with one or two copies of this variant are duns.

General Information:

  • Duns show a diluted coat color depending on their base color, and primitive markings (stripes on legs and one along the back).
  • Dun is the original coat color of all horses. Over time, two mutations (nd1 and nd2) caused the now wide-spread undiluted phenotypes most modern horses display.
  • nd1 (non-dun1) leaves the gene partially functional and allows a non-diluted coat color but may keep the primitive markings (“pseudo-duns“).
  • nd2 (non-dun2) switches the gene off completely and the horse displays a non-diluted coat color without primitive markings → most common phenotype in modern breeds.
  • A horse may be D/D, D/nd1, D/nd2, nd1/nd1, nd1/nd2, or nd2/nd2.
  • Buckskin (bay+cream) horses are often called “dun”, but a “true dun” has both a diluted coat color and primitive markings.
  • Dun is dominant, so a dun horse must have at least one dun parent.
  • A horse with a copy of cream and primitive markings from nd1 (“pseudo-dun) may be difficult to distinguish from a “true” dun.

Possible Genotypes:

Genotype: Phenotype:
Duns
D/D Dun
D/nd1 Dun
D/nd2 Dun
Pseudo-duns
nd1/nd1 undiluted coat color with primitive markings (dorsal stripe and leg bars)
nd1/nd2 undiluted coat color that may have primitive markings (dorsal stripe and leg bars):
Non-duns
nd2/nd2: undiluted coat color without primitive markings (dorsal stripe and leg bars)

 

Test information: This test detects three different variants:

1. The Wildtype (Dun).
2. The non-dun1 (nd1) mutation, which is caused by the change of a single basepair in the TBX3 gene.
3. The non-dun2 (nd2) mutation, which is caused by a deletion in 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 Online Mendelian Inheritance in Animals verfügbar.

Dun is characterized by a dilute coat color, dorsal stripe, and leg stripes (primitive markings).

Test #: H219

Samples: Blood, Hair

Price: 35 € (net)

Time required: 7-10 days

A: Dun = dilution + primitive markings
B: Pseudo-dun (nd1) = full coat color + primitive markings
C: Non-dun (nd2) = full coat color without primitive markings
D: Non-dun (nd2) + dilution factor (e.g. Cream) = diluted coat color without primitive markings
→ A “pseudo-dun” with another dilution variant will look like a “real” dun.

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