The genetics along the Silk Road: structure and evolutionary history of the populations

The understanding of the genetic structure of a population is important to describe its population history, as well as designing studies of complex biomedical traits, including disease susceptibility. The Marco Polo expedition gave us the possibilities to explore several different populations in the Caucasus and Central Asia from Georgia to Kazakhstan, obtain information on taste, and smell perception and several other phenotypes in order to identify the genetic variants implicated. Considering the stratification issue in genetic association studies the aim is to fully characterize the genetic diversity in each population in order to provide a useful array of information for future association studies. Chemosensory phenotypes like olfactory perception, taste perception, are different between and within populations and are probably the results of the combination of gene-environment interactions, for this reason finding new variants could be challenging due to the small number of individuals sampled, in addition it is worth pointing out that a large number of individuals are needed to detect genetic variants with a modest effect on the variability of a phenotype. However, as a large sample size is not always a feasible option, especially in these countries, a population-based approach is needed to take into account the population history and the genetic structure in describing phenotype variation. This thesis defines the population genetic landscape and migration pattern of the population sampled during the Marco Polo expedition and an implementation of a methodology to describe it. In addition, we used an approach based on the population to interpret and analyze the observed pattern of olfactory perception, the role of genetic variation in eye color and finally the relationship between taste perception and food preferences across different countries.