Conformational mutation in human mtDNA detected by direct sequencing of enzymatically amplified DNA

Restriction enzyme analysis of 241 human mtDNAs revealed polymorphism in the electrophoretic mobility of a fragment corresponding to part of the ND4 gene. Enzymatic amplification and direct sequencing of this fragment demonstrates that a single T--C transition correlates with the faster mobility exhibited by the fragment in seven mtDNAs from Papua New Guinea. The enhanced mobility caused by this transition could result from disrupting an AT-rich region near the middle of the fragment that might make it curve. An analogous mutation at an adjacent position in a European mtDNA causes a similar but more pronounced alteration in mobility. The seven New Guineans with this substitution are all from the Eastern Highlands Province and constitute one clade in a genealogical tree based upon restriction analysis. The additional information provided by sequencing allows refinement of the genealogical tree but does not require modification of higher order branching structure.