The DeCode team observed a rather modest linkage at a 10.5 Mb region on chromosome 10q, but decided to pursue and fine-map it thereby identifying the variant until the date showing the strongest association with T2D, an intronic variant (rs7903146) in the TCF7L2 gene contributing to, but not fully explaining, the original linkage [49,50,51]. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.