The Basques according to polymorphic Alu insertions

Polymorphic Alu insertions provide a set of DNA markers of interest in huma n population genetics. Approximately 1000-2000 of these insertions have not reached fixation within the human genome. Each one of these polymorphic lo ci most probably resulted from a unique insertional event, and therefore al l individuals possessing the insertion are related by descent not just stat e. In addition, the direction of mutational change is toward the gain of th e Alu element at a particular locus. Therefore, the improved knowledge of b oth the ancestral state and the direction of mutational change greatly faci litates the analysis of population relationships. As a result, Alu insertio n polymorphisms represent a significant tool for population genetic studies . In this study, polymorphic Alu insertions have been employed to ascertain phylogenetic relationships among Basque groups and worldwide populations. The Basques are considered to be a geographic isolate with a unique languag e and customs. They may be direct descendants of Cro-Magnon enclaves from t he upper Paleolithic (38,000 to 10,000 years). The Basques are distributed among narrow valleys in northeastern Spain with little migration between th em until recently. This characteristic may have had an effect on allelic fr equency distributions. With the aim of studying this possible effect, we ha ve analyzed six autosomal polymorphic Alu loci from four different sites wi thin the Spanish Basque region in order to ascertain any genetic heterogene ity among the Basques. The results are consistent with a lack of homogeneit y among these four autochthonous Basque groups.