To produce horses with some Arabian characteristics but coat colors not found in purebreds, they have to be crossbred with other breeds. Though the purebred Arabian produces a limited range of potential colors, they do not appear to carry any color-based lethal disorders such as the frame overo gene ("O") that can produce lethal white syndrome (LWS). Because purebred Arabians cannot produce LWS foals, Arabian mares were used as a non-affected population in some of the studies seeking the gene that caused the condition in other breeds. Nonetheless, partbred Arabian offspring can, in some cases, carry these genes if the non-Arabian parent was a carrier.