Coat formed by the combined effect of Gray and Roan on the Black base.
Typical Genetic Formula
E/_ a/a G/n Rn/n
Possible Genotype Variations
E/e a/a G/n Rn/n
E/e a/a G/n Rn/Rn
E/e a/a G/G Rn/n
E/e a/a G/G Rn/Rn
E/E a/a G/n Rn/n
E/E a/a G/n Rn/Rn
E/E a/a G/G Rn/n
E/E a/a G/G Rn/Rn
The Genetic Basis
For a horse to be born Gray Roan Black, it must receive the following combination from its parents:
- Its ability to express or produce black pigment indicates it received the dominant E allele from at least one parent.
- To be visually black, it needed to inherit the absence of Agouti (a) from both sire and dam.
- Since the Roan gene is dominant, at least one parent was necessarily Roan (Rn).
- Gray does not skip generations. For this animal to be Gray, the sire or dam had to be Gray to provide the (Rn).
Understanding the Alleles
The horse Gray Roan Black has a specific combination of alleles. Below, we explain each genetic component that forms this coat:
- 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.
- G/ (Grey): Progressive graying. Epistatic — covers all other colors.
- Rn/ (Roan): aaaaaaaaaaaaaaaa
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