ISU ANS 216 - Coat color genetics 06

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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 Principles32 pairs of chromosomes32 pairs of chromosomesGenesGenes control expression of traits and are control expression of traits and are located along chromosomelocated along chromosomeEach parent contributes Each parent contributes 50%50% of genetic makeup of genetic makeupPairs 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 PrinciplesWhen paired alleles are not identical, the horse When paired alleles are not identical, the horse is is heterozygous heterozygous at that locusat that locusWhen 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 ColorMore than 10 loci involvedMore than 10 loci involved Many epistatic effectsMany epistatic effectsAt any one locus, effects are generally due to At any one locus, effects are generally due to dominancedominanceTwo types of skin pigmentationTwo types of skin pigmentationEumelanin (black or brown)Eumelanin (black or brown)Pheomelanin (red or yellow)Pheomelanin (red or yellow)Coat Color – Extension: E eCoat Color – Extension: E eEEBlack pigmented horsesBlack pigmented horsesEither black as points or black Either black as points or black as entire coat coloras entire coat colorblacks, browns and bays, blacks, browns and bays, buckskins, duns, etcbuckskins, duns, etceeBlack pigment in skin but not in Black pigment in skin but not in hairhairHair appears redHair appears redchestnuts, red duns, chestnuts, red duns, palominos, etc.palominos, etc.E dominant to eE dominant to eEE 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 aControls the distribution pattern of black hairControls the distribution pattern of black hairRestricts dark pigment to points with ERestricts dark pigment to points with EOnly effects eumelanin (black and brown Only effects eumelanin (black and brown pigmentation)pigmentation)A dominant to aA dominant to aE_A_ = bay or brownE_A_ = bay or brownE_aa = blackE_aa = blackeeA_ 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 Genes2 main loci responsible - C and D2 main loci responsible - C and DC locusC locus - “Palomino dilution” - “Palomino dilution”CCcrcr gene is partially dominant gene is partially dominantCCcrcr - red pigmentation is diluted to - red pigmentation is diluted to yellowyellowDilutes only pheomelanin, so Dilutes only pheomelanin, so black horses are unaffectedblack horses are unaffectedFor a chestnut horse:For a chestnut horse:CC : chestnutCC : chestnutC CC Ccrcr : palomino : palominoCCcrcr C Ccrcr : cremello : cremelloFor a bay horse:For a bay horse:CC : bayCC : bayC CC Ccrcr : buckskin : buckskinCCcrcr C Ccr: cr: perlinoperlinoCremelloSire of cremelloCoat ColorCoat ColorDILUTION 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 ColorD locus D locus - “dominant dilution- “dominant dilution””Dun dilutionDun dilutionD dominant to dD dominant to dDilutes both black and red pigment on Dilutes both black and red pigment on body but not points of horsebody but not points of horseCommon to see dark points, dorsal stripe, Common to see dark points, dorsal stripe, shoulder stripe and leg barringshoulder stripe and leg barringBlack base coat:Black base coat:D_ = grullaD_ = grulladd = blackdd = blackBay base coat:Bay base coat:D_ = dunD_ = dundd = baydd = bayCoat ColorCoat ColorD locusD locusChestnut base coat:Chestnut base coat:D_ = red dunD_ = red dundd = chestnutdd = chestnutDuns usually have a Duns usually have a dorsal stripe, buckskins dorsal stripe, buckskins do notdo notWhite – W wWhite – W wInability to form pigment in Inability to form pigment in skin & hairskin & hairEpistatic to all other colorsEpistatic to all other colorsTrue 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 eyesWW = lethal (in utero)WW = lethal (in utero)Ww = whiteWw = whiteww = normal colorww = normal colorAll white horse are born white All white horse are born white and have pink skinand have pink skinEyes can either be dark or blueEyes can either be dark or blueCoat Color – Gray G gCoat Color – Gray G gG_ = grayG_ = graygg = normal colorgg = normal colorBorn colored Born colored Hairs progressively Hairs progressively replaced by white hairsreplaced by white hairsMust have at least one Must have at least one gray parentgray parentHorses continue to gray Horses continue to gray with agewith ageCoat Color – Roan Rn rnCoat Color – Roan Rn rnRn Rn = “lethal theory”Rn Rn = “lethal theory”Rn rn = roanRn rn = roanrn rn = normal colorrn rn = normal colorRoan horses are born Roan horses are born roan - the number of roan - the number of white hairs does not white hairs does not increaseincreaseMust have at least one Must have at least one roan parentroan parentCoat Color – White PatternsCoat Color – White PatternsTobiano (T locus)Tobiano (T locus)T_ = spottedT_ = spottedtt = nonspottedtt = nonspottedAny base color can be spottedAny base color can be spottedCan test for alleleCan test for


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ISU ANS 216 - Coat color genetics 06

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