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The Coat Colour Dun dilution test tests for the genetic status of the TBX3 gene.

27 working days






Hair, Blood EDTA, Blood Heparin, Semen, Tissue

Mode of Inheritance


Year Published

General information

The Coat Colour Dun dilution test tests for the genetic status of the TBX3 gene. This gene has three variants (alleles); allele D is dominant over the alleles nd1 and nd2; allele nd1 is dominant over nd2. The dominant allele D results in Dun dilution with primitive markings. Allele nd1 does not dilute the coat colour of the horse, primitive markings are present but the expression is variable. Allele nd2 does not have an effect on the basic colour.

Clinical features

The Dun dilution gene lightens the coat colour of the horse by lightening the body colour, leaving the head, lower legs, mane and tail undiluted. Dun is also typically characterised by “primitive markings”, almost all dun horses possess at least the dorsal stripe, but the presence of the other primitive markings varies. Other common markings may include horizontal striping on the legs, transverse striping across the shoulders, and lighter guard hairs along the edges of a dark mane and tail.

Additional information

A horse can also carry mutations for other modifying genes which can further affect its coat colour.

Specific breeds are undefined.

This test is performed by an external laboratory. CombiBreed takes care of the mediation between you as a customer and the external laboratory. In this case, CombiBreed cannot be held liable for the behaviour of the client and/or contractor.


Pubmed ID: 26691985

Omia ID: 1972

How does it work?

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1. Select your product(s)

Select your single test, a CombiBreed Package or create your own Bundle.

2. Collect DNA sample

Collect DNA material as indicated with our products and send it to our laboratory.

3. Results

We handle your DNA sample with care and provide you with the results.

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