TCF7L2 and type 2 diabetes mellitus: Tracking of genetic polymorphisms (i.e., single nucleotide differences between individuals) has identified single nucleotide polymorphisms (SNP) in the transcription factor 7-like 2 (TCF7L2) gene located in chromosome 10q25.2–10q25.3 with strong association with T2DM and impaired insulin secretion.