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Equine Coat Color Genetics
This document summarizes equine coat color genetics. It defines key genetics terms and describes the loci and alleles that determine the major base coat colors like black, bay, chestnut and gray. It also explains the dilution genes that produce colors like buckskin, palomino and cremello. Finally, it outlines the genetics behind white patterns like overo, tobiano and sabino as well as other coat patterns like leopard complex, roan and dun. Genetic testing can be used to identify an horse's coat color and pattern genes to aid in selective breeding and check for potential genetic disorders.
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Equine Coat Color Genetics
- 1. Equine Coat Color Genetics GeneticsTerms Types of Pigments Dominant: one allele will overshadow the other Recessive: one allele cannot overshadow the other Homozygous: two of the same alleles at a locus Heterozygous: two different alleles at a locus Melanin: black or brown color Pheomelanin: red or yellow color Basic Genetics Appearance determined by genes at specific locations (loci) Alleles are alternate forms of genes Each gene has two alleles at a locus Equine Coat Colors T h e B a s e C o l o r s D i l u t i o n G e n e s W h i t e P a t t e r n s Article Cited: Julie Ann Luiz Adrian DVM (2013) Equine Color Genetics and Deoxyribonucleic Acid Testing. J Veterinar Sci Technol 4: 134. Infographic Design and Artwork: Nicole Lehman G e n e t i c T e s t i n g Black Bay Chestnut Bay Buckskin Perlino CremelloPalominoChestnut Overo Tobiano Sabino Extension (E) Locus controls Agouti (A) Locus controls even distribution of black color limitation of black color distribution Extension and Agouti Loci work together to form three major coat colors Dominant: E Recessive: e Dominant: A Recessive: a EE or Ee = black or brown ee = chestnut AA or Aa = bay or chestnut aa = black soE_aa E_A_ ee_ _ * Note: underscore (_) indicates that either allele may be present in the phenotype Gray Locus horse born non-gray and grays with age Dominant: G Recessive: g G_ = gray gg = base color White Locus horse born without skin pigment Dominant: W Recessive: w WW = lethal Ww = white ww = base color Cream Locus Lightens base color CC = no dilution CCr = single dilution CrCr = double dilution Common Examples Bay (CC) Buckskin (CCr) Palomino (CCr) Chestnut (CC) Perlino (CrCr) Cremello (CrCr) May also occur in black horses Dun Locus Lightens body; has dark leg barring and dorsal stripe Dominant: Dn Recessive: dn Dn_ = dun dndn = base color Silver Locus Mottled silver color often seen in gray horses Dominant: Z or SILV Recessive: z or silv Z_ = dapple zz = base color Newly - Discovered Dilution Genes Pearl: light skin and teal eyes, Prl_ = pearl, prlprl = base color Champagne: bronze shade with carroty spots, Ch_ = champagne, chch = base color Paint Color Patterns splash white over base colors Three major types Overo Tobiano Sabino Color over top White over top Mix of paint and roan Dominant: O Recessive: o Dominant: TO Recessive: to Dominant: Sb Recessive: sb O_ = overo oo = base color TO_ = tobiano toto = base color Sb_ = sabino sbsb = base color Leopard Complex Appaloosa color pattern: varied levels of white spotting over base color Dominant: Lp Recessive: lp Lp_= appaloosa lplp = base color Roan Locus White and based colored hair intermixed, occurs on all base colors and dilutions Dominant: Rn Recessive: rn Rn_= roan rnrn = base color Uses: • Reduces guesswork in breeding • DNA-typing • Parentage tests • Check for genetic disorders • Especially Overo Lethal White Syndrome (OO genotype linked to lethal WW genotype)