Sire Bay on dam Roan Palomino
In this article, we will explore the genetic possibilities of coat colors for the crossing between a stallion Bay and a mare Roan Palomino. Equine genetics is a universe of combinations where dominant and recessive alleles determine the final coat of each individual.
On one side, we have the stallion Bay. Genetically, it presents the base genotype E/_ A/_. Brown body with black mane, tail, lower legs and ear tips, due to the presence of black pigment restricted to the points by the Agouti gene.
On the other side, the mare Roan Palomino contributes with its genetics based on e/e Cr/n Rn/n. The (Rn) gene acts on the base coat by distributing white hairs throughout the body, giving it a roan appearance. The head and legs retain the original base color tones. This coat is based on Palomino.
Quando combinamos esses códigos genéticos, criamos uma matriz de probabilidades. É importante lembrar que o resultado visual (fenótipo) muitas vezes esconde genes recessivos que podem pular uma geração.
The Genotypes Involved
For a horse to have the coat Bay. it carries specific gene combinations. The possible genotypes for the sire include variants such as: E/e A/a, E/e A/A, E/E A/a, E/E A/A.
As for the dam, being Roan Palomino, may present in its DNA the alleles: e/e A/A Cr/n Rn/n, e/e A/A Cr/n Rn/Rn, e/e A/a Cr/n Rn/n, e/e A/a Cr/n Rn/Rn, e/e a/a Cr/n Rn/n, e/e a/a Cr/n Rn/Rn.
Understanding the Alleles
To understand the result of this crossing, note the gene sets at play:
- e/e (Red Factor - Homozygous Recessive): Determines the inability to produce black pigment, resulting in an exclusively red base coat (Chestnut).
- E/ (Extension - Dominant): The Extension gene controls eumelanin (black) production. At least one E allele allows the horse to have black hairs.
- A/ (Agouti - Dominant): The Agouti gene controls black distribution. The A allele restricts black pigment to the points (mane, tail, legs).
- a/a (Non-Agouti - Recessive): Allows black pigment to spread uniformly across the body. Essential for Solid Black (if E/).
- Cr/n (Heterozygous Cream): One copy of the dilution allele. Lightens red pigment to gold (e.g. Palomino, Buckskin).
- Rn/ (Roan - Rosilho): Mixes white hairs throughout the body, keeping head and extremities in the original color.
Calculated Probabilities
Being the sire Bay with genotype (E/e A/a), it transmits the (E) allele (black factor) to 50% and the (e) allele (red factor) to the other 50% and transmits the (A) allele (restriction) to 50% and the (a) allele (no restriction) to the other 50%.
Being the sire Bay with genotype (E/e A/A), it transmits the (E) allele (black factor) to 50% and the (e) allele (red factor) to the other 50% and transmits the (A) allele to 100% of offspring, restricting black pigment to the extremities.
Being the sire Bay with genotype (E/E A/a), it transmits the (E) allele to 100% of offspring, enabling black pigment production (eumelanin) and transmits the (A) allele (restriction) to 50% and the (a) allele (no restriction) to the other 50%.
Being the sire Bay with genotype (E/E A/A), it transmits the (E) allele to 100% of offspring, enabling black pigment production (eumelanin) and transmits the (A) allele to 100% of offspring, restricting black pigment to the extremities.
Being the dam Roan Palomino with genotype (e/e A/A Cr/n Rn/n), it transmits the (e) allele to 100% of offspring, allowing only red pigment expression (phaeomelanin) and transmits the (A) allele to 100% of offspring, restricting black pigment to the extremities and has a 50% chance of transmitting the Cream dilution allele (Cr) and has a 50% chance of transmitting the Roan allele (Rn).
Being the dam Roan Palomino with genotype (e/e A/A Cr/n Rn/Rn), it transmits the (e) allele to 100% of offspring, allowing only red pigment expression (phaeomelanin) and transmits the (A) allele to 100% of offspring, restricting black pigment to the extremities and has a 50% chance of transmitting the Cream dilution allele (Cr) and always transmits the Roan allele (Rn).
Being the dam Roan Palomino with genotype (e/e A/a Cr/n Rn/n), it transmits the (e) allele to 100% of offspring, allowing only red pigment expression (phaeomelanin) and transmits the (A) allele (restriction) to 50% and the (a) allele (no restriction) to the other 50% and has a 50% chance of transmitting the Cream dilution allele (Cr) and has a 50% chance of transmitting the Roan allele (Rn).
Being the dam Roan Palomino with genotype (e/e A/a Cr/n Rn/Rn), it transmits the (e) allele to 100% of offspring, allowing only red pigment expression (phaeomelanin) and transmits the (A) allele (restriction) to 50% and the (a) allele (no restriction) to the other 50% and has a 50% chance of transmitting the Cream dilution allele (Cr) and always transmits the Roan allele (Rn).
Based on a standard scenario, the statistical chances for foals from this crossing are:
Roan BuckskinOpen Coat ➜ 13,8%
BuckskinOpen Coat ➜ 13,8%
Roan BayOpen Coat ➜ 12,4%
BayOpen Coat ➜ 12,4%
Roan PalominoOpen Coat ➜ 9,4%
PalominoOpen Coat ➜ 9,4%
Roan ChestnutOpen Coat ➜ 9,4%
ChestnutOpen Coat ➜ 9,4%
Roan Smoky BlackOpen Coat ➜ 1,9%
Smoky BlackOpen Coat ➜ 1,9%
Roan BlackOpen Coat ➜ 1,9%
BlackOpen Coat ➜ 1,9%
Roan Dark BrownOpen Coat ➜ 1,4%
Dark BrownOpen Coat ➜ 1,4%
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