Lactase is a small intestinal enzyme which hydrolyses lactose, the main carbohydrate in milk.
In many humans lactase activity declines after weaning whilst in others lactase persists into adulthood. This difference is genetically determined. Lactase persistence, as this is called, allows satisfactory digestion of significant quantities of fresh milk and is common in Northern Europeans and certain African and Arabian normadic tribes. We are interested in both the evolutionary and medical aspects of this trait and we are using biochemical, molecular genetic and population genetic approaches to investigate its molecular basis. This is a phosphorimage of part of the DNA sequence of the lactase gene.