HorseCoatColoursPresentation2008.pdf

Horse Coat Colours

Colours and

and

Horse Coat

Markings

Cindy Harper

Onderstepoort Laboratory for Applied

Laboratory for Applied

Veterinary Genetics

Onderstepoort

Veterinary Genetics

Basic Colours

Colours

Basic

Black

Chestnut

Bay

Genetic Control of the Basic Colours

Colours

Genetic Control of the Basic

produce melanin pigment

 2 Pigments responsible for coat and skin

Melanocytes produce melanin pigment

 Melanocytes

2 Pigments responsible for coat and skin

colour

colour – eumelanin

eumelanin (black and brown) and

(black and brown) and

phaeomelanin (red and yellow)

(red and yellow)

phaeomelanin

Colour genes control either the pigment

genes control either the pigment

producing cell or pigment production

 Colour

producing cell or pigment production

 2 genes control the main

2 genes control the main colour

colour switches

switches

in horses

Extension (E) and Agouti (A)

in horses

Extension (E) and Agouti (A)

Genetics

Locus (address of a gene and each has a

name) occurs on a pair of chromosomes – 1

from sire and 1 from dam

Sire

Dam

Form of gene (allele) on 1 chromosome of pair

can be same as on other – homozygosity

Or different – heterozygosity

Different – dominant and recessive where 1

allele is expressed and other is not

Function: Gene that codes for protein

Protein: Effect e.g. stimulates melanocyte to

produce eumelanin

Chromosome pair

Result: Black horse

The Extension Gene/Locus (E)

Difference between black and red lies in the action of 1

gene

 Difference between black and red lies in the action of 1

MC1R

 Allele symbols are E and e

gene – MC1R

Allele symbols are E and e

E extends black (

E extends black ( eumelanin

eumelanin ) in coat

) in coat

e extends red ( phaeomelanin

) in coat

Combination of alleles at the extension locus:

phaeomelanin ) in coat

e extends red (

Combination of alleles at the extension locus:

Allows black in the coat: Black, brown, bay,

buckskin,

Allows black in the coat: Black, brown, bay,

buckskin, grullo

grullo

Black in the skin but not in the coat: Chestnut,

palomino

Black in the skin but not in the coat: Chestnut,

palomino

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