MTDNA AND THE ORIGIN OF CAUCASIANS - IDENTIFICATION OF ANCIENT CAUCASIAN-SPECIFIC HAPLOGROUPS, ONE OF WHICH IS PRONE TO A RECURRENT SOMATICDUPLICATION IN THE D-LOOP REGION

mtDNA sequence variation was examined in 175 Caucasians from the Unite d States and Canada by PCR amplification and high-resolution restricti on-endonuclease analysis. The majority of the Caucasian mtDNAs were su bsumed within four mtDNA lineages (haplogroups) defined by mutations t hat are rarely seen in Africans and Mongoloids. The sequence divergenc e of these haplogroups indicates that they arose early in Caucasian ra diation and gave raise to modern European mtDNAs. Although ancient, no ne of these haplogroups is old enough to be compatible with a Neandert hal origin, suggesting that Home sapiens sapiens displaced H. s. neand erthaliensis, rather than mixed with it. The mtDNAs of one of these ha plogroups have a unique homoplasmic insertion between nucleotide pair (np) 573 and np 574, within the D-loop control region. This insertion makes these mtDNAs prone to a somatic mutation that duplicates a 270-b p portion of the D-loop region between np 309 and np 572. This finding suggests that certain nonpathogenic mtDNA mutations could predispose individuals to mtDNA rearrangements.