Genetic analysis of uniparental and autosomal markers in human populations

Zusammenfassung

The main objectives of this thesis are to describe the distribution of genetic diversity in modern human populations and the distribution across subpopulations, with emphasis on the populations of Africa and Europe, with a special focus on Cameroon, West and Central Africa, and Italy, respectively, and also, of. inferring prehistoric and historical events that determined the observed diversity and structure in contemporary populations. Most of the genome is biparentally inherited and recombines. However, two particular segments of the DNA are inherited from one parent only and do not recombine: the mtDNA and, for the most of its length, the Y chromosome.In this work, samples from Europe and Africa have been analyzed for Y chromosome, mtDNA and autosomal markers. The characterization of the distribution of genetic variation within different populations in different regions of the world, allows us to investigate the genetic affinities, or even phylogenetic proximity, within and between populations. The study of how genetic variability distributes among and within populations is a key aspect for association studies in disease studies, as well as for forensic genetic purposes. In this latter case, the study of genetic variability is essential for individual identification through a genetic 'fingerprint', i.e. a set of markers can be so variable that the observed allelic combination are nearly individual specific. The process of inference, based on models of population genetics, is strongly motivated by anthropological interest in the history of our species, their origins, movements and population development. Also forensic genetics, the science that combines population genetics and forensic medicine, is using the genetic variability of humans. In this case we have two main applications: 1) the individual identification in criminal cases and 2) the identification of two close relatives. The genetic makeup of an individual cannot be considered in isolation, but has to be related to the degree and structure of genetic variation present in the population to which that individual belongs. The employed methods of DNA typing, in fact, cannot guarantee that the given genotype is unique and that there is no other person carrying the same markers. Because of this, probabilities are computed: e.g., the probability that a person has left a biological sample in the criminal scene, or the probability that the presumed father is the biological father of a child. Estimating the probabilities is based on knowing the genotype frequencies of the population, to which the people involved in the case, belong.