Equine Science Mr Dieckhoff HORSE COLOR GENETICS BASIC

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 � Partial = Black; bb = Red; Bb = Black 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_aa. CCcr)

GENE C : CREAM DILUTION � Controls � Ccr dilution of red pigment dilutes any coat color � Pale cream with pink skin and blue eyes

GENE C : CREAM DILUTION � Cremello (ee Ccr) � Will always produce buckskins, palominos, or smoky blacks � Perlino (E_A_Ccr. Ccr) � Will always produce buckskins, palominos, or smoky blacks � Smoky Cream (E_aa. Ccr)

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_aa. CCdd : black � E_aa. CCD_: grulla / grullo � Bay base coat � E_A_CCdd: bay � E_A_CCD_: bay dun or buckskin dun � Chestnut base coat � ee. CCdd: chestnut � ee. CCD_: 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 � ee. NN: chestnut � ee. Ch_: “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_aa. NN: black � E_aa. Ch_: “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 � ee. NN or NPrl: chestnut � ee. Prl: pale apricot color of body, mane, and tail

COLOR CALCULATOR � http: //www. animalgenetics. us/CCalculator 1. a sp � http: //www. vgl. ucdavis. edu/services/coatcolo r. php

APPLICATION (21 POINTS, 3 PTS EA) � Determine 1. 2. 3. 4. 5. 6. 7. 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 Ccr dd rnrn NN ww gg ee aa CC Dd Rn. Rn 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 Ccr dd rnrn NN 2. ww Gg Ea CC Dd Rnrn ZZ 3. ww gg ee aa CC Dd rnrn Prl

ANSWERS 1. 2. 3. Buckskin, Palomino, or Smokey Black Flea Bitten Gray Chestnut with apricot body, mane, tail