ANALYSES OF MITOCHONDRIAL DNA POLYMORPHISMS IN SKELETAL REMAINS AND EXTANT POPULATIONS OF NORTHERN CHILE

Abstract

DNA studies of extinct groups make it possible to complete or confirm those carried out on current populations. In the case of the American extreme South, other Amerinds migrated to the zone in re cent times mainly to exploit economic resources. The degree to which they intermixed with each other and with the Fueguians that survived extinction, if any did, is unknown. The development of the PCR technique has greatly facilitated the analysis of the genetic mate rial of our ancient samples. The current study analy ses the conclusions of an analysis of nineteen se quences from the Hypervariable Region of mtDNA Control obtained from our ancient samples (be tween 4,000 and 200 years a.P.), mainly dental pieces, of extinct individuals of the different Fu eguian and Patagonian aborigines. This genetic marker is very useful for our purpose because it is inherited exclusively from the mother, the absence of recombination and its high mutation rate, which generates the necessary variability for distinguish ing populations. The DNA is extracted by the usual molecular biology procedures with a few particularities. The samples were crushed in a liquid nitrogen refriger ated grinder, washed with an EDTA 0.5 M and di gested with Proteinase . Then the DNA was ex tracted with Phenol/Chloroform and was concen trated with Centricon-30 microconcentrators. Fi nally fragments corresponding to the mtDNA Hy pervariable Region I were amplified and sequenced with specific primers yielding a PCR product of 273 pairs of bases. Previous studies have identified four main mi tochondrial haplogroups among Amerinds, called A, B, C and D. Some of the differences observed with respect to the referred sequence (Anderson) correspond to mutations that are characteristic of haplogroup C and D, the only two observed among the aborigines of Tierra del Fuego and Patagonia. The analysis of variability of the obtained sequences was performed within the context of the current Amerind populations published by other authors. The genetic dissimilarity between the sequences was calculated by the Kimura-2 distance param eters and, then, generating affinity trees by means of neighbour-joining and UPGMA methods respec tively (not shown). An extremely meticulous previous study indi cated, after considering almost 500 trees, that the C and D individuals studied here were separated in 97% of all the trees studied . This confers a robust basis to