The ability to digest significant quantities of the dissacharide lactose is dependent upon high expression of the enzyme lactase in the small intestine. Downregulation of lactase occurs in the vast majority of adult mammals, and most humans lose the ability to produce high levels of lactase after weaning (lactase non-persistence) whereas others keep high levels into adult life (lactase persistence). This variation in adult enzyme expression is under genetic control, and frequencies of the two phenotypes vary in throughout the world. A correlation between a longstanding culture of dairying and a high frequency of lactase persistent individuals in a population group has been reported. This has led to the theory that the high levels of lactase persistence seen in some groups could be the result of natural selection. This thesis examines variation in and around the lactase gene in to explore the possible role of natural selection in explaining modern frequencies of lactase persistence. A series of single nucleotide polymorphisms (SNPs) in the vicinity of the lactase gene have alleles known to associate with lactase persistence in Northern Europe. These were investigated in a series of4024 individuals from 73 population groups throughout the world to generate a global distribution that could be compared with anthropological data, and previously reported frequencies of lactase persistence. One of these SNPs, a C-T transition located - 13.9kb upstream of the lactase gene, was reported during the course of this thesis, (Enattah et al 2002), with the T allele proposed as a putative cause of lactase persistence. The haplotypic background of this allele is reported here.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:423090 |
| Date | January 2006 |
| Creators | Mulcare, Charlotte |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1445708/ |
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