Schematic representation of the region between the two highlighted genetic markers that is associated with adult-type hypolactasia (Enattah and colleagues). Vertical bars within the MCM6 gene represent the exons, the widths indicating relative size. The two associated single base polymorphisms (SNPs) lie within the indicated introns of the MCM6 gene which is located 5’ to the LCT (lactase-phlorizin hydrolase) gene on human chromosome 2. The arrows indicate the direction of gene transcription (the centromeric region of the chromosome is located to the left). The scale bar at the bottom of the figure indicates the size of the DNA region occupied by the MCM6 gene. The numbers at introns 13 and 9 indicate the positions of the SNPs relative to the transcriptional start site of lactase (redrawn from Enattah and colleagues20).