Coat Color and Pattern in English Shepherds

Sable and white
The shaded (or true) sable pattern is regulated by the dominant allele at the "Agouti" gene locus. Dogs that inherit at least one allele for sable pattern will have black tipping on tan/yellow hair. The amount of black shading present in the coat may vary from very little (noticeable only around ears, muzzle, tail), to quite a lot. Some people feel that dogs who are heterozygous at the Agouti locus, with one allele for sable and one for tanpoint pattern (black/tan), will be more heavily shaded, whereas dogs that carry two alleles for sable will be only lightly shaded with black.

The white pattern markings are due to recessive alleles at the white spotting locus (S). The distribution and extent of white markings varies depending on which alleles a dog inherits (Irish, piebald, or extreme). Dogs with two Irish alleles will have "typical" white patterm markings; dogs with one Irish and one piebald or extreme white allele will be "white factored"; dogs with two piebald or extreme white alleles will have "excess white".

Thomas' Char-Gin Boston