Coat genetics
Hidden coat genes: why a foal can surprise you
By Hoofprint Valley ·
A horse’s visible coat does not reveal every allele it can pass on. Understand recessive chestnut and the difference between genotype and appearance.
A coat is an expression, not a complete gene list
Genotype describes inherited alleles; phenotype describes observable traits. A horse can carry an allele without visibly expressing it. That distinction makes pedigrees and recorded genetic information useful when planning a pairing.
At Extension, the common E allele permits black pigment, while two copies of the recessive e allele give a chestnut base. An Ee horse can pass e even though it is not chestnut-based. Other genes still influence its final appearance.
Two carriers, four possible combinations
In the simple Ee × Ee example, each parent can pass E or e. The resulting probabilities are 25% EE, 50% Ee and 25% ee. These probabilities apply independently to each conception. Four foals do not have to match those proportions.
An EE or Ee result alone does not specify black or bay. Agouti affects where black pigment is distributed. Dilutions, grey and white patterns can change what you see without removing the underlying Extension alleles.
Why appearances can be misleading
Chestnut-based horses can carry Agouti alleles without showing black points. Extensive white spotting can obscure base color, while grey changes hair color with age. A photograph is therefore not a substitute for a genetic test in real horses.
Hoofprint Valley shows inherited coat information read-only. Use it alongside ancestry rather than guessing every allele from the portrait. The game’s breed-specific pools and simplified pattern coverage remain simulation choices, not laboratory predictions.
A useful breeding habit
Before choosing a pair, separate three questions: what each horse visibly expresses, which alleles are recorded, and which combinations those parents can pass on. Review the foal as one possible outcome—not proof that the odds have changed.
For real horses, consult qualified veterinary professionals and appropriate genetic testing. Coat goals should never replace health and welfare considerations.