Linkage disequilibrium and demographic history of the isolated population of the Faroe Islands

The isolated population of the Faroe Islands has a history of recent expansion after being limited to a small size for centuries. Such an isolated population may be ideal for linkage disequilibrium mapping of disease genes if linkage disequilibrium (LD) extends over large regions. Analyses of 18 markers on 12q24.3, spanning a region of 4.3 Mb (16 cM), revealed extensive LD in the Faroese population. Maximum LD was found between marker pairs separated by more than 3.8 Mb. The same region had a maximum LD of only 1.2 and 1.4 Mb respectively in two outbred Danish and British populations analysed here for comparison. The analyses of gene diversity excess at 15 unlinked microsatellite markers did not reveal any sign of a severe bottleneck to have occurred within approximately 1200 years' history of the Faroese population. The extensive LD in this population may, therefore, have arisen primarily by random genetic drift. The implications for future gene mapping studies are discussed.