These studies, published before the advent of NGS, modelled: (1) testing for mutations in KCNJ11 or ABCC8 in hypothetical 6-year-old patients with permanent neonatal diabetes; or (2) testing for mutations in HNF1A, HNF4A or GCK in hypothetical newly diagnosed MODY patients at 25 to 40 years of age, otherwise presumed to have type 2 diabetes. The gene discussed is GCK; the disease is MODY.