Genetic Identification
Genetically, smoky blacks are black horses heterozygous for the cream gene. The mutation that produces the cream colors is on the MATP gene on equine chromosome 21 (ECA21), and is an incomplete dominant trait. Incomplete dominant traits differ from recessive traits, which are only "visible" in the homozygous state, and simple dominant traits, which are just as "visible" in the homozygous or heterozygous state. Instead, the MATP mutation is visible the heterozygous state, but more so in the homozygous state. The difficulty in identifying smoky blacks has led some to describe black as "masking" cream, however smoky blacks are more properly termed "cryptic creams."
The location of the cream gene was published in 2003 and there now exists a DNA test for the cream gene. This test enables breeders to identify cryptic creams such as smoky blacks, dark palominos and buckskins, and creams whose coats are obscured by the action of the gray gene or pattern genes such as pinto.
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