Sire Gray Chestnut on dam Roan Chestnut
In this article, we will explore the genetic possibilities of coat colors for the crossing between a stallion Gray Chestnut and a mare Roan Chestnut. 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 Gray Chestnut. Genetically, it presents the base genotype e/e G/n. The (G) gene acts on the base coat promoting progressive lightening throughout the horse's life until reaching very pale or completely white tones. This coat is based on Chestnut.
On the other side, the mare Roan Chestnut contributes with its genetics based on e/e 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 Chestnut.
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 Gray Chestnut. it carries specific gene combinations. The possible genotypes for the sire include variants such as: e/e A/A G/n, e/e A/A G/G, e/e A/a G/n, e/e A/a G/G, e/e a/a G/n, e/e a/a G/G.
As for the dam, being Roan Chestnut, may present in its DNA the alleles: e/e A/A Rn/n, e/e A/A Rn/Rn, e/e A/a Rn/n, e/e A/a Rn/Rn, e/e a/a Rn/n, e/e a/a 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).
- 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/).
- G/ (Grey - Tordilho): Causes progressive greying. It is epistatic (covers other colors).
- Rn/ (Roan - Rosilho): Mixes white hairs throughout the body, keeping head and extremities in the original color.
Calculated Probabilities
Being the sire Gray Chestnut with genotype (e/e A/A G/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 Grey allele (G).
Being the sire Gray Chestnut with genotype (e/e A/A G/G), 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 always transmits the Grey allele (G).
Being the sire Gray Chestnut with genotype (e/e A/a G/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 Grey allele (G).
Being the sire Gray Chestnut with genotype (e/e A/a G/G), 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 always transmits the Grey allele (G).
Being the dam Roan Chestnut with genotype (e/e A/A 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 Roan allele (Rn).
Being the dam Roan Chestnut with genotype (e/e A/A 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 always transmits the Roan allele (Rn).
Being the dam Roan Chestnut with genotype (e/e A/a 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 Roan allele (Rn).
Being the dam Roan Chestnut with genotype (e/e A/a 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 always transmits the Roan allele (Rn).
Based on a standard scenario, the statistical chances for foals from this crossing are:
Gray Roan ChestnutOpen Coat ➜ 25,0%
Roan ChestnutOpen Coat ➜ 25,0%
Gray ChestnutOpen Coat ➜ 25,0%
ChestnutOpen Coat ➜ 25,0%
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