Genetic Chaos

Tuesday, December 14, 2004

Y chromosomal heritage of Croatian population and its island isolates

Y chromosome variation in 457 Croatian samples was studied using 16 SNPs/indel and eight STR loci. High frequency of haplogroup I in Croatian populations and the phylogeographic pattern in its background STR diversity over Europe make Adriatic coast one likely source of the recolonization of Europe following the Last Glacial Maximum. The higher frequency of I in the southern island populations is contrasted with higher frequency of group R1a chromosomes in the northern island of Krk and in the mainland. R1a frequency, while low in Greeks and Albanians, is highest in Polish, Ukrainian and Russian populations and could be a sign of the Slavic impact in the Balkan region. Haplogroups J, G and E that can be related to the spread of farming characterize the minor part (12.5%) of the Croatian paternal lineages. In one of the southern island (Hvar) populations, we found a relatively high frequency (14%) of lineages belonging to P*(xM173) cluster, which is unusual for European populations. Interestingly, the same population also harbored mitochondrial haplogroup F that is virtually absent in European populations – indicating a connection with Central Asian populations, possibly the Avars.

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The evidence of mtDNA haplogroup F in a European population and its ethnohistoric implications

Mitochondrial DNA polymorphism was analysed in a sample of 108 Croatians from the Adriatic Island isolate of Hvar. Besides typically European varieties of human maternal lineages, haplogroup F was found in a considerable frequency (8.3%). This haplogroup is most frequent in southeast Asia but has not been reported before in Europe. The genealogical analysis of haplogroup F cases from Hvar suggested founder effect. Subsequent field work was undertaken to sample and analyse 336 persons from three neighbouring islands (Brac, Korcula and Krk) and 379 more persons from all Croatian mainland counties and to determine if haplogroup F is present in the general population. Only one more case was found in one of the mainland cities, with no known ancestors from Hvar Island. The first published phylogenetic analysis of haplogroup F worldwide is presented, applying the median network method, suggesting several scenarios how this maternal lineage may have been added to the Croatian mtDNA pool.

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Homogeneity and distinctiveness of Polish paternal lineages revealed by Y chromosome microsatellite haplotype analysis

Different regional populations from Poland were studied in order to assess the genetic heterogeneity within Poland, investigate the genetic relationships with other European populations and provide a population-specific reference database for anthropological and forensic studies. Nine Y-chromosomal microsatellites were analysed in a total of 919 unrelated males from six regions of Poland and in 1,273 male individuals from nine other European populations. AMOVA revealed that all of the molecular variation in the Polish dataset is due to variation within populations, and no variation was detected among populations of different regions of Poland. However, in the non-Polish European dataset 9.3% (P<0.0001) of the total variation was due to differences among populations. Consequently, differences in RST-values between all possible pairs of Polish populations were not statistically significant, whereas significant differences were observed in nearly all comparisons of Polish and non-Polish European populations. Phylogenetic analyses demonstrated tight clustering of Polish populations separated from non-Polish groups. Population clustering based on Y-STR haplotypes generally correlates well with the geography and history of the region. Thus, our data are consistent with the assumption of homogeneity of present-day paternal lineages within Poland and their distinctiveness from other parts of Europe, at least in respect to their Y-STR haplotypes.

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Differentiation and Genetic Position of Slavs among Eurasian Ethnic Groups as Inferred from Variation in Mitochondrial DNA

The distribution of identical and similar (phylogenetically related) types of hypervariable segment1 (HVS1) of the mitochondrial DNA (mtDNA) was studied in human populations belonging to three Slavonic groups and nine ethnogeographic groups of Eurasia (total sample size 2772 people). The results testified to a common origin of West, South, and East Slavs and revealed a central place of West Slavs among all Slavonic ethnic groups. Mixing was shown to play a substantial role in the formation of specific features of all three Slavonic gene pools. The mitochondrial gene pools of the Slavonic ethnic groups proved to preserve features suggesting a common ancestor for these and South European populations (especially those of the Balkan Peninsula).

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Mitochondrial DNA variability in Poles and Russians

Mitochondrial DNA (mtDNA) sequence variation was examined in Poles (from the Pomerania-Kujawy region; n=436) and Russians (from three different regions of the European part of Russia; n=201), for which the two hypervariable segments (HVS I and HVS II) and haplogroup-specific coding region sites were analyzed. The use of mtDNA coding region RFLP analysis made it possible to distinguish parallel mutations that occurred at particular sites in the HVS I and II regions during mtDNA evolution. In total, parallel mutations were identified at 73 nucleotide sites in HVS I (17.8%) and 31 sites in HVS II (7.73%). The classification of mitochondrial haplotypes revealed the presence of all major European haplogroups, which were characterized by similar patterns of distribution in Poles and Russians. An analysis of the distribution of the control region haplotypes did not reveal any specific combinations of unique mtDNA haplotypes and their subclusters that clearly distinguish both Poles and Russians from the neighbouring European populations. The only exception is a novel subcluster U4a within subhaplogroup U4, defined by a diagnostic mutation at nucleotide position 310 in HVS II. This subcluster was found in common predominantly between Poles and Russians (at a frequency of 2.3% and 2.0%, respectively) and may therefore have a central-eastern European origin.

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