Tree of 39 mtDNA sequences belonging to haplogroup U. The tree, rooted using the reference sequence (rCRS) (Andrews et al. 1999) as an outgroup, illustrates subhaplogroup affiliations. The sequencing procedure and phylogeny construction were performed as described elsewhere (Torroni et al. 2001b; Achilli et al. 2004). For phylogeny construction, the highly variable site 16519 and the length variation in the poly-C stretch at nts 309–315 were not used, and half the weight was assigned to the control-region mutations, relative to that assigned to coding-region mutations. Mutations are shown on the branches; they are transitions, unless a base change is explicitly indicated. Insertions are suffixed with a plus sign (+) and the inserted nucleotide(s), and deletions have a “d” prefix. Recurrent mutations are underlined; pathological mutations are in italics. The ethnic/geographic origins of mtDNAs are as follows: Pakistan (1–3, 12, and 13), Spain (4, 8, 14, 23, 36, and 39), Yemen (5 and 7), Adygei (6, 10, 18, and 20), Italy (9, 15–17, 19, 21, 22, 24, 31–33, 35, and 37), Ethiopia (11 and 38), Berber (30 and 34), Saami (25, 26, and 28), Yakut (27), and Fulbe from Senegal (29).