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Equine Coat Color Genetics Jenny Ingwerson

Equine Coat Color Genetics Jenny Ingwerson. Basic Principles. 32 pairs of chromosomes Genes control expression of traits and are located along chromosome Each parent contributes 50% of genetic makeup

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Equine Coat Color Genetics Jenny Ingwerson

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  1. Equine Coat Color GeneticsJenny Ingwerson

  2. Basic Principles • 32 pairs of chromosomes • Genes control expression of traits and are located along chromosome • Each parent contributes 50% of genetic makeup • Pairs of genes at the same physical location (locus) on a chromosome are called alleles

  3. Basic Principles • When paired alleles are not identical, the horse is heterozygous at that locus • When paired alleles are identical, the horse is homozygous at that locus

  4. Qualitative Coat Color • More than 10 loci involved • Many epistatic effects • At any one locus, effects are generally due to dominance • Two types of skin pigmentation • Eumelanin (black or brown) • Pheomelanin (red or yellow)

  5. Coat Color – Extension: E e • E • Black pigmented horses • Either black as points or black as entire coat color • blacks, browns and bays, buckskins, duns, etc • e • Black pigment in skin but not in hair • Hair appears red • chestnuts, red duns, palominos, etc. • E dominant to e • EE or Ee = black or bay (or brown) • ee = chestnut

  6. Coat Color - AGOUTI: A a • Controls the distribution pattern of black hair • Restricts dark pigment to points with E • Only effects eumelanin (black and brown pigmentation) • A dominant to a • E_A_ = bay or brown • E_aa = black • eeA_ or eeaa = chestnut • **Chestnuts • like any recessive, will always breed true • chestnut x chestnut = chestnut

  7. Coat Color – Dilution Genes • 2 main loci responsible - C and D • C locus - “Palomino dilution” • Ccr gene is partially dominant • Ccr - red pigmentation is diluted to yellow • Dilutes only pheomelanin, so black horses are unaffected • For a chestnut horse: • CC : chestnut • C Ccr : palomino • Ccr Ccr : cremello • For a bay horse: • CC : bay • C Ccr : buckskin • Ccr Ccr: perlino Cremello Sire of cremello

  8. Coat Color • DILUTION GENES (cont.) • C locus - “Palomino dilution” • This is why palominos do not breed true! CCcr x CCcr • 25%CC 50% CCcr 25% Ccr Ccr Not diluted Palomino or buckskin Cremllo or Perlino

  9. Coat Color • D locus - “dominant dilution” • Dun dilution • D dominant to d • Dilutes both black and red pigment on body but not points of horse • Common to see dark points, dorsal stripe, shoulder stripe and leg barring • Black base coat: • D_ = grulla • dd = black • Bay base coat: • D_ = dun • dd = bay

  10. Coat Color • D locus • Chestnut base coat: • D_ = red dun • dd = chestnut • Duns usually have a dorsal stripe, buckskins do not

  11. White – W w • Inability to form pigment in skin & hair • Epistatic to all other colors • True albinos have a white coat, mane, and tail, with pink skin and pink eyes • WW = lethal (in utero) • Ww = white • ww = normal color • All white horse are born white and have pink skin • Eyes can either be dark or blue

  12. Coat Color – Gray G g • G_ = gray • gg = normal color • Born colored • Hairs progressively replaced by white hairs • Must have at least one gray parent • Horses continue to gray with age

  13. Coat Color – Roan Rn rn • Rn Rn = “lethal theory” • Rn rn = roan • rn rn = normal color • Roan horses are born roan - the number of white hairs does not increase • Must have at least one roan parent

  14. Coat Color – White Patterns • Tobiano (T locus) • T_ = spotted • tt = nonspotted • Any base color can be spotted • Can test for allele • Overo (frame) • Was thought to be recessive, but now determined dominant • Appaloosa - unclear inheritance • Markings - probably due to many genes

  15. Rules • It usually takes at least one light-colored parent to produce a light-colored foal. • Chestnut and sorrel, when mated to one another, can produce only more chestnuts and sorrels. • Bay mated to bay, black or chestnut/sorrel can produce bay, chestnut, sorrel, and, rarely, black. • Black mated to black produces black (or, rarely, chestnut or sorrel). • Black mated to bay will usually produce a bay, fairly commonly produces chestnut or sorrel, and only rarely produces black. • Black mated to chestnut will usually produce bay, but also chestnut or sorrel, and, rarely, black. Color prediction is never 100 percent accurate.

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