Smutty
Smutty (also sooty ) is the name of a gene that changes the color of a horse by interfering with black hair.
Horses with this gene look like they have dark stains on their backs. Sometimes the gene can lead to “appling” on a colored background. In other animals it creates a pseudo eel line .
Browns with this gene can easily be confused with black-browns, but their color is caused by a variant of the agouti locus. Since this agouti allele has not been known for a long time, it is to be expected that many black-browns will still be incorrectly referred to as obscured by sooty.
Foxes with the gene differ from the uniformly dark brown dark foxes in their differently colored hair.
genetics
The Smutty gene is represented by Sty. It causes black hair to mix in with the brown or fox-colored fur. The gene has a dominant effect, i.e. horses that have the gene only once look like horses that have it on both alleles. The exact location of the gene and its equivalents in other animal species are unknown.