Human mitochondrial DNA variability: multidisciplinary applications in the fields of forensic, medical and population genetics

espanolGracias a las peculiaridades que presenta el ADN mitocondrial (multiples copias por celula, herencia materna, ausencia de recombinacion, alta tasa de mutacion), el analisis de su variabilidad pudo ser aplicado, en la presente tesis, a diferentes campos de estudio: En el campo de la genetica de poblaciones: permitio analizar el origen y la dispersion de las poblaciones humanas modernas En el campo de la genetica forense: permitio investigar muestras forenses degradadas o sin ADN nuclear (como huesos y cabellos sin bulbo). En el campo de la genetica clinica: permite la identificacion de posibles mutaciones que pueden causar una enfermedad o participar de ella; ademas de detectar una posible estratificacion en los estudios caso-control que podria suponer el establecimiento de una relacion erroneas entre una variante genetica y una enfermedad. En el presente proyecto de tesis, ademas del desarrollo de un protocolo para la obtencion del genoma mitocondrial completo, se han desarrollado diferentes metodos de minisecuenciacion, que consisten en la incorporacion de una sola base en una posicion conocida que presenta variabilidad entre individuos, como son SNaPShot (Applied Biosystems, Foster City, CA, USA) que detecta la variante por fluorescencia o por primera vez por medio de MALDI-TOF MS (Sequenom, San Diego, CA, USA) que detecta la variante por espectrometria de masas. EnglishThe results of the present project indicate that the analysis of the mtDNA variation can be useful in medical, forensic, and population genetic studies. The particular features of the mtDNA, including high copy number, lack of recombination, and high average mutation rate; also determine its usefulness and limitations in genetic studies. For instance, the reconstruction of the phylogeny is straightforward because the lineages are passed through the matriline with the only changes generated by mutation. However, this is a single marker and only tells the history of female population, which not necessarily match the demography of the whole population. We have applied these principles to the analysis of several human populations, to the forensic field, and to some medical study. All of them have many aspects in common, indicating also the important interplay that should be always needed in all mtDNA studies. For instance, one cannot carry out a forensic or medical genetic study ignoring population variation patterns or the important heterogeneity that exists regarding site specific mutation rates. We have contributed to improve our knowledge of the variation in several African, European, and American populations. In this project we have also focussed our attention in several aspects of forensic interest, concerning the analysis of degraded and low DNA amount samples. And finally, we have tried to establish a necessary bridge between the different fields of research, indicating that proper quality standards can help to avoid false positives of instabilities in cancer studies, erroneous conclusions in forensic casework, or errors in datasets that could have consequences in population studies or indirectly in forensic or medical genetic ones.