1. ¹Department of Forensic Medicine, University of Helsinki, Helsinki, Finland
2. ²Forensic Genetic Paternity Testing Unit, National Institute of Health and Welfare, Helsinki, Finland
3. ³Department of Molecular Medicine, National Institute of Health and Welfare, Helsinki, Finland

Correspondence: Dr JU Palo, Department of Forensic Medicine, PO BOX 40, University of Helsinki, FIN-00014 Helsinki, Finland. Tel: +358 9 191 27471; Fax: +358 9 191 27518; E-mail: jukka.palo@helsinki.fi

Received 28 October 2008; Revised 11 February 2009; Accepted 26 February 2009; Published online 15 April 2009.

Abstract

The Finnish population in Northern Europe has been a target of extensive genetic studies during the last decades. The population is considered as a homogeneous isolate, well suited for gene mapping studies because of its reduced diversity and homogeneity. However, several studies have shown substantial differences between the eastern and western parts of the country, especially in the male-mediated Y chromosome. This divergence is evident in non-neutral genetic variation also and it is usually explained to stem from founder effects occurring in the settlement of eastern Finland as late as in the 16th century. Here, we have reassessed this population historical scenario using Y-chromosomal, mitochondrial and autosomal markers and geographical sampling covering entire Finland. The obtained results suggest substantial Scandinavian gene flow into south-western, but not into the eastern, Finland. Male-biased Scandinavian gene flow into the south-western parts of the country would plausibly explain the large inter-regional differences observed in the Y-chromosome, and the relative homogeneity in the mitochondrial and autosomal data. On the basis of these results, we suggest that the expression of 'Finnish Disease Heritage' illnesses, more common in the eastern/north-eastern Finland, stems from long-term drift, rather than from relatively recent founder effects.