This gene determines whether the horse will have any black pigment in its coat
Breeds known to carry this mutation
Red pigment (e) is recessive to black pigment (E)
Inheritance of the base colours of chestnut, bay and black is dependent on two genes. The first is MC1R which will determine whether black pigment is expressed. The dominant allele (variant) is indicated with a capital E and allows black pigment on the coat. The recessive allele (e/e) prevents black pigment, so the horse is chestnut. When mated, two chestnuts can only ever produce chestnut foals.
Interpretation of results
e/e: Horse is homozygous for the recessive chestnut allele. The horses base colour is chestnut.
E/e: Horse is heterozygous for the recessive chestnut allele. The horses base colour is bay or black.
E/E: Horse has no copies of the recessive chestnut allele. The horses base colour is bay or black.
Marklund et al. A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat colour in horses. Mammalian Genome 1996; 7: 895-899