Population structure of Qataris in comparison to HGDP world populations. (A) Principal components 1 and 2 of all 55 HGDP populations along with Qataris colored by sampling origin. The Qataris, in orange, can roughly be divided into three sub-populations by general ancestry determined by PCA, STRUCTURE (see additional file 2) and SupportMix: squares, Arabic-Qataris; triangles, Persian-Qataris; diamonds, African-Qataris. Three sample individuals, one from each sub-population, are identified by arrows; Q1 from Arab-Qataris, Q2 from Persian-Qataris and Q3 from African-Qataris. (B) Sample locations of a subset of HGDP populations in region of world that showed significant similarity to the Qatari samples. Several European, Asian and all populations from the Americas and Oceania are outside the ploted region. (C) Locus-specific ancestry estimates of 156 Qatari individuals for chromosomes 1, 2 and 3 as determined by SupportMix. Each individual is shown as two vertical bars, one for each haploid genome where regions (from start of the chromosomes at the top to the end of chromosomes at bottom) are colored by the most similar ancestral HGDP population as indicated by color-legend and sample location in B. The three individuals in panel A are also indicated in panel C by arrows. Results of the entire autosomal genome are presented in additional file 2 along with estimates from STRUCTURE.