 A DNA test can now identify the "Lp" gene, though a combination of pedigree knowledge and coat characteristics also help.While both heterozygous and homozygous "Lp" horses possess the aforementioned characteristics, heterozygotes and homozygotes differ significantly in the presence of true spots.True leopard spots are produced only by the "Lp" gene, and directly reflect the underlying coat color (bay, black, gray, cremello, red dun, and so on).