This is directly from UC Davis:
Sabino is a generic description for a group of similar white spotting patterns. The sabino pattern is described as irregular spotting usually on the legs, belly and face, often with extensive roaning. A mutation has recently been discovered that produces one type of sabino pattern. It has been named Sabino1 as it is not present in all sabino-patterned horses. More mutations will probably be identified that account for other sabino patterns.
Sabino1 is inherited as an autosomal dominant mutation. One copy of the Sabino1 gene is expected to produce horses with two or more white legs or feet -- often with white running up the anterior part of the leg, an extensive blaze, spotting on the midsection, with jagged or roaned margins to the pattern. Horses with 2 copies of the Sabino1 gene, are at least 90% white and are referred to as Sabino-white.
Sabino1 is most commonly found in Tennessee Walking Horses. Other breeds in which this mutation has been found include: American Miniature Horses, American Paint Horses, Aztecas, Missouri Foxtrotters, Shetland Ponies, Spanish Mustangs and Pony of the Americas. Other breeds of horses that are known to have sabino patterns, such as Clydesdales and Arabians, have so far tested negative for the Sabino1 mutation, although the number of animals tested is low.
The results for the test are reported as:
N/N No evidence of altered sequence detected.
N/SB1: One copy of the Sabino1 gene detected. Horse typically may have 2 or more white legs, blaze, spots or roaning in the midsection and jagged margins around white areas.
SB1/SB1 Two copies of the Sabino1 gene detected. Complete or nearly complete white phenotype expected.
