What is the gene that causes horses to change colour?

There's no single gene responsible for all horse coat color changes. It's a complex interaction of multiple genes, each influencing a specific aspect of pigment production and distribution.

Here's a simplified breakdown:

* Extension (E) gene: Controls the primary pigment, either black (E) or red (e).

* Agouti (A) gene: Modifies the distribution of the primary pigment, leading to bay (A), chestnut (a), or other variations.

* Cream (Cr) gene: Dilutes the primary pigment, resulting in palomino (Cr), buckskin (Cr), or other dilutions.

* Dun (D) gene: Adds primitive markings like dorsal stripe and leg barring, with varying intensity.

* Champagne (CH) gene: Dilutes the primary pigment and affects eye color.

* Gray (G) gene: Causes progressive graying of the coat, usually starting as a foal.

These are just some of the key genes involved, and there are other factors influencing the final coat color. For example, the pattern genes, like Leopard Complex (LP) and Sabino (SB) genes, determine markings like spots and roaning.

Therefore, understanding a horse's coat color requires knowing the specific combination of alleles for each gene it carries.

This complexity makes horse coat genetics fascinating and a popular field of study.