Coat colour G locus / Grey (STX17-related) - Horse

Grey and the G locus in horses

This DNA test examines the G locus for grey coat colour in horses. It detects a STX17 duplication that causes the dominant grey allele. The trait is also known as Grey, gray, G locus or progressive greying of the coat.

Horses with the grey allele are often born dark or coloured and gradually lose pigment in the hair. The final coat can become very light or nearly white, while skin pigment and the original base-colour genotype remain genetically present.

Inheritance and result

• N/N means the dominant grey allele was not detected.
• N/G / G/G means the horse carries one or two copies of the grey allele. The test does not distinguish one copy from two copies.

Practical value of this test

The result helps breeders and owners predict early whether a foal or young horse will progressively grey. This supports colour planning, sale expectations, registration, breeding selection and interpretation of the underlying base colour when the visible coat later becomes much lighter.