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Human mitochondrial DNA variation and the origin of Basques
J Bertranpetit1, J Sala, F Calafell
1Laboratori d'Antropologia, Facultat de Biologia, Universitat de Barcelona, Spain.
Annals of Human Genetics
|January 1, 1995
Summary
The Basque population likely originated from a few founding lineages that diversified rapidly. Mitochondrial DNA (mtDNA) analysis reveals unique genetic sequences and suggests a significant demographic expansion occurred tens of thousands of years ago.
Area of Science:
- Population Genetics
- Human Evolutionary Studies
- Mitochondrial DNA Analysis
Background:
- The Basque population is known for its genetic distinctiveness compared to other European groups.
- Mitochondrial DNA (mtDNA) control region sequences offer insights into population history and maternal lineage. Hypervariable Segment I (HV1) is frequently used for such studies.
Purpose of the Study:
- To investigate the genetic origins and demographic history of the Basque population using mtDNA HV1 sequences.
- To identify unique genetic markers within the Basque population and compare their genetic diversity with other human populations.
Main Methods:
- PCR amplification and sequencing of the mtDNA hypervariable segment I (positions 16024-16383) from 45 unrelated individuals of Basque descent.
- Analysis of sequence variation, pairwise differences, and phylogenetic reconstruction (most parsimonious tree, neighbor-joining tree).
- Comparison of Basque mtDNA sequences with other published population data using Nei & Miller genetic distances.
Main Results:
- Twenty-seven distinct mtDNA HV1 sequences were identified in the Basque sample, with 21 being unique.
- A low mean pairwise nucleotide difference (3-15) and a low number of steps for the most parsimonious tree suggest a bottleneck event and rapid diversification.
- Pairwise difference distribution supports a demographic expansion between 14,500 and 42,000 years Before Present.
- While classical markers distinguish Basques, mtDNA HV1 sequences showed them clustering with other Caucasoid samples, unlike more distant African samples.
Conclusions:
- The Basque population appears to have been founded by a small number of lineages that diverged rapidly.
- Evidence suggests a significant demographic expansion in the Basque population during the Upper Paleolithic period.
- mtDNA HV1 analysis does not reveal the same level of distinctiveness for Basques compared to other European populations as observed with classical genetic markers.