Relative to its biological function, in a study in postmortem brains from Japanese patients with schizophrenia, Okuyama et al (1999), showed that the presence of the T allele (rs1800955), compared with the C allele, reduces the transcriptional efficiency of DRD4 by 40% [18]; however, failed to replicate this finding using cell culture assays [19]. The gene discussed is DRD4; the disease is schizophrenia.