 Some breed registries select against white, while others select for it; the result is that, prior to the ability to map the horse genome and perform DNA testing to verify parentage, assorted rules were created to delineate "spotted" from "non-spotted".The rules were not based on the behavior of known white spotting genes and many organizations have yet to catch up to modern understanding of genetics.Two horses with identical genotypes for a particular white spotting pattern may phenotypically be considered "solid" or "spotted", depending on the amount of patterning that is visible.