FROM ASIA TO EUROPE - MITOCHONDRIAL-DNA SEQUENCE VARIABILITY IN BULGARIANS AND TURKS

Two hypervariable sequence segments in the control region of mitochond rial DNA were determined in samples of Bulgarians and Turks. The Turki sh sample presented a higher degree of internal diversity, in terms of total number of variable nucleotides, as well as in the average pairw ise nucleotide difference. Pairwise difference distributions were buil t for both samples, yielding smooth bell shapes in agreement with the Rogers and Harpending model. The Bulgarian and Turkish data were compa red with several European and W. Asian Caucasoid populations (Basques, Tuscans, Sardinians. British, Middle Easterners and Indians). Mean pa irwise differences suggest that a demographic expansion occurred seque ntially in the Middle East, through Turkey, to the rest of Europe (Bul garia included). Current mutation rate estimates date this expansion i n times ranging between 50000 and 100000 years ago and, thus, would co rrespond to the arrival of anatomically modern humans in Europe. Seque nce trees for segment I show that European and Middle Eastern sequence s derived from the reference sequence. Coalescence times for segment I sequences agree with those predicted by pairwise distributions. Genet ic trees were constructed between populations and revealed an extreme homogeneity between European samples.