Based on our hypothesis that DA-related genes are important in male-only affected sib-pair families[18], we examined four markers at the DRD2 locus that are commonly used to investigate possible associations between DAergic function and behavioural abnormalities[38], and three polymorphisms at the PPP1R1B locus to determine whether there was an association of these DA-related genes with autism. The gene discussed is DRD2; the disease is autism.