Horse Color Genetics - Harrisonville Schools
Equine Science Mr. Dieckhoff HORSE COLOR GENETICS BASIC GENETICS Heredity Process of passing traits on to offspring Genes The basic unit of inheritance A DNA sequence at a specific location on a chromosome, occur in pairs CHROMOSOMES Human – 23 pairs (46 total) Chicken – 39 pairs (78 total) Cattle – 30 pairs (60 total) Sheep – 27 pairs (54 total) Swine – 19 pairs (38 total) Horse – 32 pairs (64 total) Donkey – 31 pairs (62 total) Mule – 63 total TERMINOLOGY Locus Region of chromosome where particular gene is carried Allele Alternative forms of gene at locus Genotype Pair of alleles at given locus Actual genetic makeup of individual TERMINOLOGY Homozygous Same alleles at both loci Heterozygous Different alleles at both loci Phenotype Expression of alleles, what they look like MODES OF GENE ACTION Complete Dominance One allele “masks” expression of another Ex: black coat color in angus cattle BB = Black; bb = Red; Bb = Black Partial or Incomplete Dominance One allele does not completely “mask” expression of another allele Ex: coat color in Shorthorn cattle RR = Red; rr = White; Rr = Roan PUNNETT’S SQUARE If two roan shorthorns are bred, what are expected genotypes and phenotypes of their progeny? QUALITATIVE COAT COLOR More than 10 loci involved At any one locus, effects are generally due to dominance Two types of skin pigmentation Eumelanin (black or brown) Pheomelanin (red or yellow) GENE W : WHITE Can mask all other genes W dominant to w WW : lethal Ww : true white Pink ww: skin and white hair not white Color depends on other genes GENE G : GRAY G dominant to g G_: gray All gray horses must have one gray parent Flea-bitten grays are probably Gg gg: not gray GENE E : EUMELANIN (BLACK HAIR) E dominant to e E_: black hair (whole body or points) Black, ee: brown, bay, buckskin, etc. red hair Sorrel, chestnut, palomino, etc. GENE A : AGOUTI (BLACK POINTS) Controls distribution of black hair (E_) E_A_ Black points; bay E_aa Black Ee body, black, brown aa / ee A_ Chestnut, sorrel GENE C : CREAM DILUTION Controls dilution of red pigment CC: full pigment CCcr: yellow body Bay = buckskin (E_A_CCcr) Sorrel = palomino (ee CCcr) Black = smoky black (E_aaCCcr) GENE C : CREAM DILUTION Controls dilution of red pigment CcrCcr dilutes any coat color Pale cream with pink skin and blue eyes GENE C : CREAM DILUTION Cremello (ee CcrCcr) Will always produce buckskins, palominos, or smoky blacks Perlino (E_A_CcrCcr) Will always produce buckskins, palominos, or smoky blacks Smoky Cream (E_aaCcrCcr) GENE D : DUN GENE Dilutes both black and red coat color, but not dark points Characteristics Darker points Dorsal stripe Shoulder stripe Leg barrrings D dominant to d GENE D : DUN DILUTION Black base coat E_aaCCdd : black E_aaCCD_: grulla / grullo Bay base coat E_A_CCdd: bay E_A_CCD_: bay dun or buckskin dun Chestnut base coat eeCCdd: chestnut eeCCD_: red dun GENE Rn: ROAN Rn is dominant to rn Rn__: roan rn rn: non roan Must have at least one roan parent GENE Ch : CHAMPAGNE DILUTION Dominant Gene Must have at least one Champagne parent Controls dilution of hair from black to brown and red to gold Skin is lavender and speckles with age Eye are amber GENE Ch : CHAMPAGNE DILUTION Chestnut base coat eeNN: chestnut eeCh_: “gold” often with flaxen mane & tail Bay base coat E_A_NN: bay E_A_Ch_: “amber”; tan with black points Black base coat E_aaNN: black E_aaCh_: “classic”; darker tan with brown points GENE Z : SILVER DILUTION Dominant gene Must have one silver parent Controls dilution of black pigment NN: full pigment NZ or ZZ: Sorrel: no effect Bay: lightened pigment on lower legs and flaxen mane and tail Black: chocolate with flaxen mane and tail GENE Prl : PEARL DILUTION Formerly “Barlink Dilution” Recessive gene Only seen in chestnuts Can interact with Cream Chestnut base coat eeNN or NPrl: chestnut eePrlPrl: pale apricot color of body, mane, and tail COLOR CALCULATOR http://www.animalgenetics.us/CCalculator1.as p http://www.vgl.ucdavis.edu/services/coatcolor. php APPLICATION (21 POINTS, 3 PTS EA) 1. 2. 3. 4. 5. 6. 7. Determine the color patterns of the following horses: ww gg ee aa CC dd rnrn NPrl Ww Gg Ee aa CCcr dd rnrn NN ww gg Ee Aa CC dd rnrn NN ww gg Ee aa CC Dd rnrn NN ww gg EE AA CC dd rnrn ZZ ww gg ee aa CcrCcr dd rnrn NN ww gg ee aa CC Dd RnRn NN ANSWERS (21 POINTS, 3 PTS EA) 1. 2. 3. 4. 5. 6. 7. Chestnut or sorrel White Bay Gurlla / Grullo Chocolate with flaxen mane & tail Palomino or Cremello Red Roan Dun QUIZ (9 POINTS) 1. ww gg ee aa CcrCcr dd rnrn NN 2. ww Gg Ea CC Dd Rnrn ZZ 3. ww gg ee aa CC Dd rnrn PrlPrl ANSWERS 1. 2. 3. Buckskin, Palomino, or Smokey Black Flea Bitten Gray Chestnut with apricot body, mane, tail
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