Sire Dun Dark Brown on dam Chestnut
In this article, we will explore the genetic possibilities of coat colors for the crossing between a stallion Dun Dark Brown and a mare 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 Dun Dark Brown. Genetically, it presents the base genotype E/_ A/_ D/n. The Dun gene acts on the base color, adding the characteristic dark dorsal stripe. In some cases it lightens the body tone and may also produce zebra-like leg markings. This coat is based on Dark Brown.
On the other side, the mare Chestnut contributes with its genetics based on e/e. Base coat with a reddish body, mane and tail, with no black pigment.
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 Dun Dark Brown. it carries specific gene combinations. The possible genotypes for the sire include variants such as: E/e A/a D/n, E/e A/a D/D, E/e A/A D/n, E/e A/A D/D, E/E A/a D/n, E/E A/a D/D, E/E A/A D/n, E/E A/A D/D.
As for the dam, being Chestnut, may present in its DNA the alleles: e/e A/A, e/e A/a, e/e a/a.
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/).
- D/ (Dun - Primitive Gene): Dilutes body color and adds dorsal stripe and leg barring.
Calculated Probabilities
Being the sire Dun Dark Brown with genotype (E/e A/a D/n), 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% and has a 50% chance of transmitting the primitive Dun allele (D).
Being the sire Dun Dark Brown with genotype (E/e A/a D/D), 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% and always transmits the primitive Dun allele (D).
Being the sire Dun Dark Brown with genotype (E/e A/A D/n), 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 and has a 50% chance of transmitting the primitive Dun allele (D).
Being the sire Dun Dark Brown with genotype (E/e A/A D/D), 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 and always transmits the primitive Dun allele (D).
Being the dam Chestnut with genotype (e/e A/A), 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.
Being the dam Chestnut with genotype (e/e A/a), 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%.
Being the dam Chestnut with genotype (e/e a/a), it transmits the (e) allele to 100% of offspring, allowing only red pigment expression (phaeomelanin) and transmits the (a) allele to 100% of offspring, allowing black to spread in homozygosis (if Extension is present).
Based on a standard scenario, the statistical chances for foals from this crossing are:
Dun BayOpen Coat ➜ 25,4%
BayOpen Coat ➜ 25,4%
Dun ChestnutOpen Coat ➜ 17,5%
ChestnutOpen Coat ➜ 17,5%
GrulloOpen Coat ➜ 4,3%
BlackOpen Coat ➜ 4,3%
Dun Dark BrownOpen Coat ➜ 2,8%
Dark BrownOpen Coat ➜ 2,8%
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