The (To) gene acts on the base coat forming large, well-defined white patches across the body and legs. Many cases also inherit blue eyes. This coat is based on Chestnut.
Typical Genetic Formula
e/e To/n
Possible Genotype Variations
e/e A/A To/n
e/e A/A To/To
e/e A/a To/n
e/e A/a To/To
e/e a/a To/n
e/e a/a To/To
The Genetic Basis
For a horse to be born Paint Chestnut, it must receive the following combination from its parents:
- To have the red base (Chestnut), this animal necessarily inherited a recessive (e) allele from the sire and another from the dam. Both parents carried the red factor.
- The Tobiano patches that characterize the Paint Horse were inherited from at least one parent.
Understanding the Alleles
The horse Paint Chestnut has a specific combination of alleles. Below, we explain each genetic component that forms this coat:
- e/e (Red Factor): The animal has a fundamentally red base (Chestnut), due to the total absence of black pigment.
- A/ (Agouti): The Agouti gene, when active (with E present), restricts black pigment to the extremities. Carried with no visual effect in e/e animals.
- a/a (Non-Agouti): Allows black to spread over the entire body when combined with E. In e/e animals it is invisible but still passed on.
- To/ (Tobiano): Vertical white patches crossing the back.
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