equine genetics calculator

How this equine genetics calculator works

This calculator models Mendelian inheritance across three independent loci commonly used as a starting point in horse color prediction. For each parent, you pick a genotype at each locus. The tool then creates all possible allele combinations, calculates probabilities, and maps those genotypes to likely phenotype names.

Genes included in this version

• Extension (E/e): Controls whether black pigment can be produced. Horses with e/e are in the red/chestnut family.
• Agouti (A/a): Restricts black pigment to points (mane, tail, legs) when black pigment is available. This distinguishes bay family from black family in E/_ horses.
• Cream (N/Cr): Incomplete dominant dilution gene. One copy produces single dilution (e.g., palomino, buckskin), two copies produce double dilution (e.g., cremello, perlino).

Phenotype mapping used by the calculator

The model uses the following practical mapping rules:

• Base color from Extension + Agouti:
  • e/e → Chestnut base
  • E/_ + A/_ → Bay base
  • E/_ + a/a → Black base
• Then apply Cream:
  • Chestnut + N/Cr → Palomino, Chestnut + Cr/Cr → Cremello
  • Bay + N/Cr → Buckskin, Bay + Cr/Cr → Perlino
  • Black + N/Cr → Smoky Black, Black + Cr/Cr → Smoky Cream

Example breeding scenario

If both parents are E/e, A/a, and N/Cr, the foal can inherit a wide range of combinations. This is a classic setup where you may get chestnut-based, bay-based, or black-based outcomes, each with no cream, one cream, or two cream copies depending on random gamete pairing.

Important limitations (read before making decisions)

Real horse color genetics can be more complex than a three-locus model. This calculator is best treated as a quick planning aid, not a guarantee.

• It does not currently include Gray, which can progressively mask underlying coat color.
• It does not include pattern genes like Tobiano, Frame Overo, Splash, or Sabino.
• It does not model modifiers such as sooty, flaxen, or seasonal/fading effects.
• It assumes equal viability of genotypes and independent assortment for modeled loci.

Best practices for breeders

• Use panel testing from reputable equine genetics labs.
• Track both genotype and observed phenotype in your records.
• Prioritize health, temperament, structure, and welfare over color alone.
• When in doubt, consult a veterinary geneticist or equine reproduction specialist.