Equine Coat Color Genetics Jenny IngwersonBasic PrinciplesSlide 3Qualitative Coat ColorCoat Color – Extension: E eCoat Color - AGOUTI: A aCoat Color – Dilution GenesCoat ColorSlide 9Slide 10White – W wCoat Color – Gray G gCoat Color – Roan Rn rnCoat Color – White PatternsRulesEquine Coat Color Equine Coat Color GeneticsGeneticsJenny IngwersonJenny IngwersonBasic PrinciplesBasic Principles32 pairs of chromosomes32 pairs of chromosomesGenesGenes control expression of traits and are control expression of traits and are located along chromosomelocated along chromosomeEach parent contributes Each parent contributes 50%50% of genetic makeup of genetic makeupPairs of genes at the same physical location Pairs of genes at the same physical location (locus) on a chromosome are called (locus) on a chromosome are called allelesallelesBasic PrinciplesBasic PrinciplesWhen paired alleles are not identical, the horse When paired alleles are not identical, the horse is is heterozygous heterozygous at that locusat that locusWhen paired alleles are identical, the horse is When paired alleles are identical, the horse is homozygoushomozygous at that locus at that locusQualitative Coat ColorQualitative Coat ColorMore than 10 loci involvedMore than 10 loci involved Many epistatic effectsMany epistatic effectsAt any one locus, effects are generally due to At any one locus, effects are generally due to dominancedominanceTwo types of skin pigmentationTwo types of skin pigmentationEumelanin (black or brown)Eumelanin (black or brown)Pheomelanin (red or yellow)Pheomelanin (red or yellow)Coat Color – Extension: E eCoat Color – Extension: E eEEBlack pigmented horsesBlack pigmented horsesEither black as points or black Either black as points or black as entire coat coloras entire coat colorblacks, browns and bays, blacks, browns and bays, buckskins, duns, etcbuckskins, duns, etceeBlack pigment in skin but not in Black pigment in skin but not in hairhairHair appears redHair appears redchestnuts, red duns, chestnuts, red duns, palominos, etc.palominos, etc.E dominant to eE dominant to eEE or Ee = black or bay (or EE or Ee = black or bay (or brown)brown)ee = chestnutee = chestnutCoat Color - Coat Color - AGOUTI: A aAGOUTI: A aControls the distribution pattern of black hairControls the distribution pattern of black hairRestricts dark pigment to points with ERestricts dark pigment to points with EOnly effects eumelanin (black and brown Only effects eumelanin (black and brown pigmentation)pigmentation)A dominant to aA dominant to aE_A_ = bay or brownE_A_ = bay or brownE_aa = blackE_aa = blackeeA_ or eeaa = chestnuteeA_ or eeaa = chestnut**Chestnuts**Chestnuts like any recessive, will always like any recessive, will always breed truebreed truechestnut x chestnut = chestnutchestnut x chestnut = chestnutCoat Color – Dilution GenesCoat Color – Dilution Genes2 main loci responsible - C and D2 main loci responsible - C and DC locusC locus - “Palomino dilution” - “Palomino dilution”CCcrcr gene is partially dominant gene is partially dominantCCcrcr - red pigmentation is diluted to - red pigmentation is diluted to yellowyellowDilutes only pheomelanin, so Dilutes only pheomelanin, so black horses are unaffectedblack horses are unaffectedFor a chestnut horse:For a chestnut horse:CC : chestnutCC : chestnutC CC Ccrcr : palomino : palominoCCcrcr C Ccrcr : cremello : cremelloFor a bay horse:For a bay horse:CC : bayCC : bayC CC Ccrcr : buckskin : buckskinCCcrcr C Ccr: cr: perlinoperlinoCremelloSire of cremelloCoat ColorCoat ColorDILUTION GENES (cont.)DILUTION GENES (cont.)C locus - “Palomino dilution” C locus - “Palomino dilution” This is why palominos do not breed true!This is why palominos do not breed true! CCCCcrcr x CC x CCcrcr 25%CC 25%CC 50% CC 50% CCcrcr 25% C25% Ccr cr CCcrcrPalomino or buckskin Cremllo or PerlinoNot dilutedCoat ColorCoat ColorD locus D locus - “dominant dilution- “dominant dilution””Dun dilutionDun dilutionD dominant to dD dominant to dDilutes both black and red pigment on Dilutes both black and red pigment on body but not points of horsebody but not points of horseCommon to see dark points, dorsal stripe, Common to see dark points, dorsal stripe, shoulder stripe and leg barringshoulder stripe and leg barringBlack base coat:Black base coat:D_ = grullaD_ = grulladd = blackdd = blackBay base coat:Bay base coat:D_ = dunD_ = dundd = baydd = bayCoat ColorCoat ColorD locusD locusChestnut base coat:Chestnut base coat:D_ = red dunD_ = red dundd = chestnutdd = chestnutDuns usually have a Duns usually have a dorsal stripe, buckskins dorsal stripe, buckskins do notdo notWhite – W wWhite – W wInability to form pigment in Inability to form pigment in skin & hairskin & hairEpistatic to all other colorsEpistatic to all other colorsTrue True albinoalbinos have a white coat, s have a white coat, mane, and tail, with pink skin mane, and tail, with pink skin and pink eyesand pink eyesWW = lethal (in utero)WW = lethal (in utero)Ww = whiteWw = whiteww = normal colorww = normal colorAll white horse are born white All white horse are born white and have pink skinand have pink skinEyes can either be dark or blueEyes can either be dark or blueCoat Color – Gray G gCoat Color – Gray G gG_ = grayG_ = graygg = normal colorgg = normal colorBorn colored Born colored Hairs progressively Hairs progressively replaced by white hairsreplaced by white hairsMust have at least one Must have at least one gray parentgray parentHorses continue to gray Horses continue to gray with agewith ageCoat Color – Roan Rn rnCoat Color – Roan Rn rnRn Rn = “lethal theory”Rn Rn = “lethal theory”Rn rn = roanRn rn = roanrn rn = normal colorrn rn = normal colorRoan horses are born Roan horses are born roan - the number of roan - the number of white hairs does not white hairs does not increaseincreaseMust have at least one Must have at least one roan parentroan parentCoat Color – White PatternsCoat Color – White PatternsTobiano (T locus)Tobiano (T locus)T_ = spottedT_ = spottedtt = nonspottedtt = nonspottedAny base color can be spottedAny base color can be spottedCan test for alleleCan test for
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