Sabino(SB) is an incomplete dominant gene, like Frame Overo and Cream. In Sabino's heterozygous form it creates minimal to normal white markings. In its homozygous form it creates a horse that is solid white. It is believed that any white marking not caused by any of the other "white marking genes," including splash, frame overo, tobiano, dominant white, and the appaloosa patterns, is caused by some form of sabino. It is also believed that there is more than one form of sabino.
Now, despite what many people think, horses do not need four high white stockings,a big blaze with lip spots, and belly spots to be sabino. A horse doesnt even need ONE of those things to be a sabino. Sabino can be as minimal as a sock or a star, and possibly even have no white at all. Sabino also has the ability to cause roaning on a horse, but this is not to be confused with True Roan, Rabicano, or Appaloosa Roaning.
The only sabino mutation that has been located is called Sabino 1. The researchers put the "1" after it because, like stated above, they believe there is more than one form of sabino out there. Sabino 1 is found in many breeds, but is most often found in Tennesse Walking Horses, Missouri Fox Trotters, and Miniature Horses.
These next horses are Missouri Fox Trotters from Mikarma Farms.
This is their stallion Color Master. He was used in the study for Sabino 1, and is homozygous for Sabino 1. This means he carries two copies of Sabino 1 and that every one of his offspring will have at least one copy of Sabino 1.
Here are pictures of four of his offspring. You can see just how minimal a sabino can truly be. All are heterozygous for Sabino 1