While being a dominant gene, it can only be expressed on dogs that have tan in their coat. It can show up within the tan markings on a black and tan or tri-color dog or over the whole body of a sable dog. It is described as black stripes. This gene carried by some of dogs within the Guy Wilson lines, but not all of them.
While it is a dominant gene, it is only expressed on dogs with white markings. These “freckles” or spots show up mainly on the legs and muzzles of the dogs. On an excessive white English Shepherd, it can appear over the entire body.
Split Face/White Head
This is thought to be a separate gene from the White Spotting gene, which can also affect the width and length of the blaze.
Black Mask (Em)
While it is a dominant gene, it is only expressed on dogs with tan/sable on their faces. It can be seen on sable or black and tan English Shepherds. If the dog also has a white muzzle, there may only be a thin black line of the mask showing.