This disease leads to neurological anomalies, gout and a compulsive tendency to self-mutilation. The other is haemoph!_lia and is due to deficiency of a blood clotting factor. What interests us in these pedigrees is that more males have the disorder while females are very rarely affected. (Individual IV-1 in Figure JA and 11-1 in Figure JB). This kind of a 'sex bias' in the inheritance pattern is the first clue