aDNA Studies Research Articles

Post-mortem DNA damage hotspots in Bison ( Bison bison) provide evidence for both damage and mutational hotspots in human mitochondrial DNA

Post-mortem damage-driven mutations are a phenomena associated with ancient DNA (aDNA) studies. A previous study has demonstrated that the distribution of such mutations in human mitochondrial DNA is not random, but is concentrated in ‘hotspots’ that correlate with sites of elevated mutation rate in vivo. However, as the previous study was undertaken on human samples, it is possible for a critic to argue that the results might be biased through the presence of modern contaminant DNA sequences among the ancient DNA extracts. In this study we confirm the phenomena of DNA damage hotspots using a data set that is unlikely to be affected by contamination – cloned mitochondrial control region sequences extracted from 81 ancient bison ( Bison bison). Furthermore, using published data from modern bovid specimens, we confirm that the damage hotspots correlate with sites of in vivo hypermutation. In conclusion, the aDNA sequences from archaeological specimens provide evidence that structural elements of mitochondrial DNA confer a degree of in vivo and post-mortem protection from sequence modification. This in turn provides useful insights into the debate as to whether mutational hotspots or mitochondrial recombination might best explain homoplasies observed on phylogenetic trees of human mitochondrial sequences.

Temporal Mitochondrial DNA Variation in the Basque Country: Influence of Post‐Neolithic Events

The Basque population has been considered an outlier in a large number of genetic studies, due to its hypothesized antiquity and greater genetic isolation. The present paper deals with an analysis of the mtDNA variability of the historical population of Aldaieta (VI-VII c. AD; Basque Country) which, together with genetic data existing for other prehistoric populations of the Basque Country (4,500-5,000 YBP), permits an appraisal of the hypotheses proposed for the origin of the genetic differentiation of the Basque population. Given that this is an aDNA study, application has been made both of standard precautions, to avoid contamination, and of authentication criteria (analysis of duplicates, replication in an independent laboratory, quantification of target DNA, sequencing and cloning of PCR products). The variability of the mtDNA haplogroups of the historical population of Aldaieta falls within the range of the present-day populations of Europe's Atlantic fringe, whereas the prehistoric populations of the Basque Country display clear differentiation in relation to all others. Consequently, we suggest that between 5,000-1,500 YBP approximately, there may have been gene flow amongst the western European populations that homogenised mtDNA lineages.

Application de la technique de PCR en temps réel à l’étude de l’ADN ancien

Real-time Polymerase Chain Reaction (PCR) for the study of ancient DNA. The properties of ancient DNA (aDNA) make difficult the retrieval of DNA sequence. The advantage of Real-Time PCR was exploited, for the first time, in the study of aDNA. We determined the optimal condition to amplify, in one round of PCR, aDNA, which should be directly sequenced. Beside the verification of aDNA authenticity, we compared two cleaning bone methods: scalpel and ethanol. The ethanol specimens showed the best DNA yield. The aDNA was extracted and amplified (mitochondrial hypervariable region I) from five skeletons exhumed from the archaeological site of Notre-Dame-du-Bourg (France), dated from 3rd to 17th century. To cite this article: R. Kefi et al., C. R. Palevol 2 (2003) 125–132.