Fig. (3) Hierarchical scheme recommended to identify mtDNA haplogroups. In the first step, samples are run using Single Base Extension (SBE) assay. With this approach ~85% of samples are assigned to one of the six most common mtDNA European haplogroups (H, V, K, U, T or J). Remaining samples are studied by PCR-RFLP depending on the polymorphic site 10394 (A10398G): those samples with the 10398G allele are tested for 10032AluI (+10032AluI are assigned to haplogroup I, 10029G allele), whereas those with the 10398A allele are tested for either 14465AccI (+14465AccI are assigned to haplogroup X, 14470C allele) or 8994HaeIII (-14465AccI, -8994HaeIII are assigned to haplogroup W, 14470T and 8994A alleles respectively).