The Finnish population is one of the most genetically studied in the world. A relatively small number of founder individuals and strong genetic isolation over centuries have shaped the unique genetic makeup across the country that we are now utilizing heavily in genetic studies of diseases and traits. Here, we present a fine-scale genetic structure of Finland before 1950s, thus focusing on the time before large-scale migrations and urbanization that have occurred since 1950s. These results are published and explained in more detail in G3: Genes, Genomes, Genetics.
Data and Methods: Data are from the FINRISK Study of the National Institute for Health and Welfare and contain 1,042 individuals whose both parents were born under 80 km from each other. No pairs of close relatives were included. Additionally, genetic data from 230,000 positions of the genome was utilized. Computational methods used were ChromoPainter and FineSTRUCTURE.
Maps: Each point represents one individual and is located at the mean coordinates of the parents' birthplaces. We show 17 maps that divide the individuals into groups based on genome information and shown by separate colors. The first map presents only one group and at each subsequent step one of the groups splits into two subgroups. The interpretation is that, on each map, the individuals in one group are on average more genetically similar with each other than with the individuals from the other groups. We expect that the order of splits has an approximate correspondence to the amount of genetic differentiation between the groups and the tree on the right hand side of the map shows the relationships of the groups measured by a genetic distance.
