equine coat color genetics jenny ingwerson l.
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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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basic principles
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
basic principles3
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
qualitative coat color
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)
coat color extension e e
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
coat color agouti a a
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
coat color dilution genes
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

coat color
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

coat color9
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
coat color10
Coat Color
  • D locus
    • Chestnut base coat:
      • D_ = red dun
      • dd = chestnut
    • Duns usually have a dorsal stripe, buckskins do not
white w w
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
coat color gray g g
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
coat color roan rn rn
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
coat color white patterns
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
rules
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.