Horse Coat Color Calculator
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Horse Coat Color Calculator
Determine potential offspring coat colors based on parent genetics.
Potential Offspring Coat Colors:
Enter parent genetics to see results.
Understanding Horse Coat Color Genetics
Horse coat color is a fascinating and complex field governed by genetics. Multiple genes interact to determine the base color, any dilutions, patterns, and other modifiers that result in the vast array of colors seen in horses.
Basic Genes Affecting Color:
- Extension (E) Gene: This gene controls the production of dark pigment (eumelanin).
- EE or Ee: Allows dark pigment to be produced. On a black base, results in a black horse. On a chestnut base (when aa is present), it still results in a chestnut horse because the agouti gene is required to restrict dark pigment to points.
- ee: Restricts the production of dark pigment, resulting in a chestnut (red) base coat regardless of other genes.
- Agouti (A) Gene: This gene affects the *distribution* of dark pigment (eumelanin) on horses that have the Extension gene allowing dark pigment (EE or Ee).
- AA or Aa: Restricts dark pigment to the points (mane, tail, lower legs, ear rims), resulting in a bay or brown horse if the base is black. If the base is chestnut (ee), agouti has no visible effect.
- aa: Allows dark pigment to spread uniformly over the body, resulting in a black horse if the base is black. If the base is chestnut (ee), it remains chestnut.
- Base Color Genes (e.g., Black, Chestnut, Bay): The combination of Extension and Agouti genes determines the most common base colors:
- Black: Ee or EE + aa
- Bay: Ee or EE + AA or Aa
- Chestnut: ee (regardless of Agouti genotype)
Note on Input Values:
The 'Base Color' inputs represent the combined effect of Extension (E) and Agouti (A) genes. For simplicity:
eeAA (and eeAa) represents Chestnut.EEAA (and EEAa) represents Bay.eeaa represents Black (Note: This is technically impossible in reality as 'aa' requires 'ee' to be visible, but used here for distinct input selection for black base).Eeaa (and EeaA) represents Black.
The 'Pattern Gene' inputs cover common modifiers.
Common Pattern and Modifier Genes:
- Roan (RN): Causes white hairs to mix evenly throughout the coat, often sparing the head and lower legs. Can be heterozygous (Rnrn) or homozygous (RnRn).
- Grey (G): Causes the coat color to lighten with age, eventually turning white. Can be heterozygous (Gg) or homozygous (GG).
- Dominant White (W): A dominant gene that can cause a horse to be born white or nearly white. Many different alleles exist (e.g., W20, W22), but Ww is sufficient to produce a white pattern.
- Cream (Cr): A dilution gene. Affects eumelanin and pheomelanin.
- CrCr (Double Cream): Dilutes black to cream/white (perlino/cremello) and bay to pale cream (palomino).
- Crcr (Single Cream): Dilutes black to buckskin and bay to palomino.
- Dun (D): A primitive dun factor that adds specific markings: dorsal stripe, primitive markings on the forehead, and often zebra stripes on the legs and a dark ear stripe. Dilutes the body coat but not the points.
- Champagne (Ch): Another dilution gene with distinct effects, often resulting in a golden body with a darker mane/tail, or a lighter body with a lighter mane/tail, and "coke bottle" eyes.
- Silver (Z): Dilutes only black pigment. Chestnut horses are unaffected. Black pigment becomes silver or grey. Bay pigment is diluted to a chocolate body with a flaxen mane/tail.
How the Calculator Works:
This calculator simplifies the process by using common representations of the Extension and Agouti genes for base color, and then allows for the selection of a single primary pattern gene. It simulates a Punnett square for each gene pair (base color and pattern) and combines the results to predict the most likely coat colors of the offspring.
The calculator considers the inheritance of two alleles for each gene from each parent. For example, if Parent 1 is Ee and Parent 2 is ee, the offspring have a 50% chance of inheriting E (resulting in Ee) and a 50% chance of inheriting e (resulting in ee).
Example Scenario:
Let's say Parent 1 is a Bay (EEAa) and Parent 2 is a Black (Eeaa). Both are genetically bay/black horses without special patterns.
- Extension Gene (E/e): Parent 1 (EE) can only pass E. Parent 2 (Ee) can pass E or e. Offspring will be EE (50%) or Ee (50%). All offspring can produce dark pigment.
- Agouti Gene (A/a): Parent 1 (AA) can only pass A. Parent 2 (aa) can only pass a. Offspring will all be Aa.
- Combined Base: All offspring will be EE or Ee, and all will be Aa. This combination (E_A_) results in Bay.
If Parent 1 was Bay (EeAa) and Parent 2 was Chestnut (eeaa), the possibilities would be more varied, leading to potential bay, black, or chestnut offspring.
Limitations:
This calculator provides a simplified model. Real horse color genetics involve many more genes and complex interactions. It does not account for recessive Ws, multiple dilutions, Sabino, Splashed White, or complex interactions between different pattern genes.
function calculateCoatColors() {
var parent1Color = document.getElementById("parent1Color").value;
var parent1Pattern = document.getElementById("parent1Pattern").value;
var parent2Color = document.getElementById("parent2Color").value;
var parent2Pattern = document.getElementById("parent2Pattern").value;
var resultDiv = document.getElementById("result-value");
resultDiv.innerHTML = ""; // Clear previous results
// — Base Color Calculation —
var baseColors = calculateBaseColors(parent1Color, parent2Color);
var potentialBaseColors = Object.keys(baseColors);
// — Pattern Calculation —
var potentialPatterns = calculatePatterns(parent1Pattern, parent2Pattern);
// — Combine Base and Pattern —
var finalCoatColors = [];
for (var i = 0; i < potentialBaseColors.length; i++) {
var base = potentialBaseColors[i];
for (var j = 0; j color !== "Invalid").sort();
if (finalCoatColors.length === 0) {
resultDiv.innerHTML = "Could not determine colors. Check inputs.";
} else {
resultDiv.innerHTML = finalCoatColors.join("");
}
}
function calculateBaseColors(p1Base, p2Base) {
var possibleBases = {};
// Get alleles from string representations
var p1E = p1Base.substring(0, 2); // e.g., 'ee' or 'EE'
var p1A = p1Base.substring(2, 4); // e.g., 'AA' or 'aa'
var p2E = p2Base.substring(0, 2); // e.g., 'ee' or 'EE'
var p2A = p2Base.substring(2, 4); // e.g., 'AA' or 'aa'
// Simulate Punnett Square for Extension (E/e)
var possibleE = [];
for (var e1 of p1E) {
for (var e2 of p2E) {
possibleE.push(e1 + e2);
}
}
possibleE = […new Set(possibleE)]; // Unique E genotypes
// Simulate Punnett Square for Agouti (A/a)
var possibleA = [];
for (var a1 of p1A) {
for (var a2 of p2A) {
possibleA.push(a1 + a2);
}
}
possibleA = […new Set(possibleA)]; // Unique A genotypes
// Determine actual base colors from E and A combinations
for (var eGenotype of possibleE) {
for (var aGenotype of possibleA) {
var isBlackBased = false;
if (eGenotype.includes('E')) { // If Extension allows dark pigment
isBlackBased = true;
}
var hasAgouti = false;
if (aGenotype.includes('A')) {
hasAgouti = true;
}
var baseColorName = "";
if (eGenotype.includes('ee')) { // Chestnut base
baseColorName = "Chestnut";
} else if (isBlackBased && hasAgouti) { // Black based with Agouti
baseColorName = "Bay";
} else if (isBlackBased && !hasAgouti) { // Black based without Agouti
baseColorName = "Black";
} else {
baseColorName = "Unknown"; // Should not happen with valid inputs
}
possibleBases[baseColorName] = true;
}
}
return possibleBases;
}
function calculatePatterns(p1Pattern, p2Pattern) {
var possiblePatterns = [];
var p1Alleles = p1Pattern.split(");
var p2Alleles = p2Pattern.split(");
if (p1Pattern === 'none' && p2Pattern === 'none') {
return ['none'];
}
if (p1Pattern === 'none') {
// Ensure we don't get duplicates like ['R', 'r'] for Rnrn
var uniqueP2 = […new Set(p2Alleles)];
if (uniqueP2.length === 1) return [p2Pattern]; // Homozygous
if (uniqueP2.length === 2 && uniqueP2.includes(p2Alleles[0].toLowerCase()) && uniqueP2.includes(p2Alleles[1].toLowerCase())) return [p2Pattern]; // Heterozygous correct format
return uniqueP2.sort().join(") === p2Pattern ? [p2Pattern] : [p2Pattern, p2Pattern.split(").reverse().join(")] // Handle cases like 'Gg' or 'gG'
}
if (p2Pattern === 'none') {
var uniqueP1 = […new Set(p1Alleles)];
if (uniqueP1.length === 1) return [p1Pattern]; // Homozygous
if (uniqueP1.length === 2 && uniqueP1.includes(p1Alleles[0].toLowerCase()) && uniqueP1.includes(p1Alleles[1].toLowerCase())) return [p1Pattern]; // Heterozygous correct format
return uniqueP1.sort().join(") === p1Pattern ? [p1Pattern] : [p1Pattern, p1Pattern.split(").reverse().join(")]
}
// Simplified approach for common patterns like Roan, Grey, Dominant White
// Assumes two alleles per gene, case-sensitive for dominance
var alleles1 = [];
if (p1Pattern.length === 2) alleles1 = [p1Pattern[0], p1Pattern[1]];
else if (p1Pattern.length === 4) alleles1 = [p1Pattern.substring(0,2), p1Pattern.substring(2,4)]; // For AtAt etc.
var alleles2 = [];
if (p2Pattern.length === 2) alleles2 = [p2Pattern[0], p2Pattern[1]];
else if (p2Pattern.length === 4) alleles2 = [p2Pattern.substring(0,2), p2Pattern.substring(2,4)];
var offspringAlleles = [];
for (var a1 of alleles1) {
for (var a2 of alleles2) {
var combo = [a1, a2].sort().join("); // Sort for consistency (e.g., Gg)
offspringAlleles.push(combo);
}
}
offspringAlleles = […new Set(offspringAlleles)]; // Unique allele combinations
// Map genotypes to pattern names
var patternNames = [];
offspringAlleles.forEach(function(alleleCombo) {
var patternName = 'none';
if (alleleCombo === 'RnRn' || alleleCombo === 'Rn' || alleleCombo === 'nR' || alleleCombo === 'nr') patternName = 'Roan';
else if (alleleCombo === 'Rnrn' || alleleCombo === 'Rnrn' || alleleCombo === 'rnRn' || alleleCombo === 'rn' || alleleCombo === 'nR') patternName = 'Roan'; // Heterozygous
else if (alleleCombo === 'GG' || alleleCombo === 'G' || alleleCombo === 'gG') patternName = 'Grey (Homozygous)';
else if (alleleCombo === 'Gg' || alleleCombo === 'g' || alleleCombo === 'Gg') patternName = 'Grey (Heterozygous)';
else if (alleleCombo === 'WW' || alleleCombo === 'W' || alleleCombo === 'wW') patternName = 'Dominant White (Homozygous)';
else if (alleleCombo === 'Ww' || alleleCombo === 'w' || alleleCombo === 'Ww') patternName = 'Dominant White (Heterozygous)';
else if (alleleCombo === 'AtAt' || alleleCombo === 'At' || alleleCombo === 'tA') patternName = 'Agouti (Black-based)';
else if (alleleCombo === 'Ata' || alleleCombo === 'At' || alleleCombo === 'aA') patternName = 'Agouti (Black-based)';
else if (alleleCombo === 'aa') patternName = 'Non-Agouti';
else if (alleleCombo === 'chch' || alleleCombo === 'ch') patternName = 'Chestnut Base (Recessive)';
else if (alleleCombo === 'Chch' || alleleCombo === 'Ch' || alleleCombo === 'hC') patternName = 'Chestnut Base (Heterozygous)';
else if (alleleCombo === 'CC' || alleleCombo === 'C') patternName = 'Chestnut Base (Homozygous)';
// Special handling for complex base color inputs
if (p1Pattern.includes('ee') || p2Pattern.includes('ee')) { // Chestnut base
if (alleleCombo === 'ee' || alleleCombo === 'Ee' || alleleCombo === 'EE') { /* ignore E/e if base is already chestnut */ }
}
if (p1Pattern.includes('aa') || p2Pattern.includes('aa')) { // Non-agouti
if (alleleCombo === 'aa') { /* Valid non-agouti */ }
else if (alleleCombo === 'AA' || alleleCombo === 'Aa' || alleleCombo === 'aA') { patternName = 'Bay'; } // This is a simplification, should be handled by base color calc
}
if (patternName !== 'none') patternNames.push(patternName);
});
// Add 'None' if no other pattern gene is inherited or if it was explicitly selected and no other pattern results
if (patternNames.length === 0 && (p1Pattern === 'none' || p2Pattern === 'none')) {
patternNames.push('None');
}
if (patternNames.length === 0 && p1Pattern !== 'none' && p2Pattern !== 'none'){
// If no specific pattern matched, assume base color without modification
patternNames.push('None');
}
return […new Set(patternNames)]; // Return unique pattern names
}
function applyPattern(baseColor, pattern) {
if (pattern === 'none' || pattern === 'None') {
return baseColor;
}
// Simplified application of common patterns
if (baseColor === "Chestnut") {
if (pattern.includes("Roan")) return "Chestnut Roan";
if (pattern.includes("Grey")) return "Grey (on Chestnut)";
if (pattern.includes("Dominant White")) return "White (on Chestnut)";
return baseColor; // Chestnut unaffected by Agouti or Silver
} else if (baseColor === "Bay") {
if (pattern.includes("Roan")) return "Bay Roan";
if (pattern.includes("Grey")) return "Grey (on Bay)";
if (pattern.includes("Dominant White")) return "White (on Bay)";
if (pattern.includes("Agouti")) return "Bay"; // Agouti doesn't change Bay
if (pattern.includes("Silver")) return "Chocolate (Silver Bay)";
return baseColor;
} else if (baseColor === "Black") {
if (pattern.includes("Roan")) return "Blue Roan";
if (pattern.includes("Grey")) return "Grey (on Black)";
if (pattern.includes("Dominant White")) return "White (on Black)";
if (pattern.includes("Agouti")) return "Bay"; // aa makes black, AA/Aa makes bay
if (pattern.includes("Silver")) return "Silver Black";
return baseColor;
}
return baseColor; // Default if pattern doesn't modify base
}