Population Genetics of Lactase Persistence and Lactose Intolerance

摘要: Variation in the ability of adult humans to digest lactose milk is a genetically determined trait that has excited interest many for past 50 years. The seems have risen high frequencies by one strongest selection pressures ever described. This section describes phenotypic polymorphism and evidence genetic involves regulation expression lactase gene caused multiple independent mutations reached different populations, because benefits drinking milk. evolutionary history Europe Africa are rather different; there being single high-frequency allele Europe, contrast alleles Africa. Also selective forces, which likely include both nutritional water content milk, may been these regions. Key Concepts: The enzyme, lactase, restricted small intestine where it digests suckling mammals. Lactase persists into life some, but not all, people. Lactase persistence trait, varies frequency populations world. Mutations an enhancer sequence, at distance from gene, appear be responsible persistence. These arose last few thousand years under strong positive selection. The attributable nutrients or fresh and/or its calorific value. Keywords: lactose; milk; lactase; selection; persistence; tolerance