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Locus Information: SB locus

Inheritance: incomplete autosomal-dominant

→ Incomplete means that animals with only one copy of the variant (Sb1/n) will show a less pronounced phenotype than horses with two copies of the variant (Sb1/Sb1).

General Information:

  • Heterozygotes (Sb1/n) have white patches with indistinct borders (especially on head, belly and legs).  This can be mistaken for roan ticking, or as a horse going grey.
  • Horses with two copies of the variant (homozygote) are usually completely white, and are often called “max white”.
  • Breeds commonly displaying this phenotype are: Tennesse Walking Horse, Miniature Horse, Paint Horse, Azteca Horse, Missouri Foxtrotter, Shetland Pony, Spanish Mustang and Pony of the Americas.
  • Sb1 is a special form of White Spotting/Dominant White.
  • Many horses without the SB1 mutation show an Sabino-like phenotype, due to other mutations in the KIT gene (W-variants) or other yet unknown variations.

Possible Genotypes:

Genotype: Effects:
n/n No Sabino-1 mutation.
Sb1/n The horse has one copy of the Sb1-variant → pattern with indistinct white patches and/or white on head and legs. Phenotype is very variable.
Sb1/Sb1 The horse has two copies of the Sb1-variant → often completely white coat or only small remnants of color (often ears).

 

Test information: This test detects the change of a single basepair in the KIT gene.

Brooks, S.A., Bailey, E.: Exon skipping in the KIT gene causes a Sabino spotting pattern in horses. Mamm Genome 16(11):893-902, 2005. Doi: 10.1007/s00335-005-2472-y.

Further information is available at Online Mendelian Inheritance in Animals.

Blurred edges of patches are a distinct characteristic for the Sabino pattern.

Test #: H207

Samples: Blood, Hair

Price: 35 € (net)

Time required: 7-10 days

The roan-like distribution of white hair, and white face and legs are common Sb1 traits.

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