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J Bertranpetit

Publications and source records attributed to J Bertranpetit.

At least 73 records · Page 4Linked to original sources
PubMed1997

Population history of north Africa: evidence from classical genetic markers.

After an intensive bibliographic search, we compiled all the available data on allele frequencies for classical genetic polymorphisms referring to North African populations and synthesized the data in an attempt to reconstruct the populations' demographic history using two complementary methods: (1) principal components analysis and (2) genetic distances represented by neighbor-joining trees. In both analyses the main feature of the genetic landscape in northern Africa is an east-west pattern of variation pointing to the differentiation between the Berber and Arab population groups of the northwest and the populations of Libya and Egypt. Moreover, Libya and Egypt show the smallest genetic distances with the European populations, including the Iberian Peninsula. The most plausible interpretation of these results is that, although demic diffusion during the Neolithic could explain the genetic similarity between northeast Africa and Europe by a parallel process of gene flow from the Near East, a Mesolithic (or older) differentiation of the populations in the northwestern regions with later limited gene flow is needed to understand the genetic picture. The most isolated groups (Mauritanians, Tuaregs, and south Algerian Berbers) were the most differentiated and, although no clear structure can be discerned among the different Arab- and Berber-speaking groups, Arab speakers as a whole are closer to Egyptians and Libyans. By contrast, the genetic contribution of sub-Saharan Africa appears to be small.

Africa, Northern↗
PubMed1996

Sequence diversity of the control region of mitochondrial DNA in Tuscany and its implications for the peopling of Europe.

The control region of mitochondrial DNA has been widely studied in various human populations. This paper reports sequence data for hypervariable segments 1 and 2 of the control region from a population from southern Tuscany (Italy). The results confirm the high variability of the control region, with 43 different haplotypes in 49 individuals sampled. The comparison of this set of data with other European populations allows the reconstruction of the population history of Tuscany. Independent approaches, such as the estimation of haplotype diversity, mean pairwise differences, genetic distances and discriminant analysis, place the Tuscan sample in an intermediate position between sequences from culturally or geographically isolated regions of Europe (Sardinia, the Basque Country, Britain) and those from the Middle East. In spite of the remarkable genetic homogeneity in Europe, a degree of variability is shown by local European populations and homogeneity increases with the relative isolation of the population. The pattern of mitochondrial variation in Tuscany indicates the persistence of an ancient European component subsequently enriched by migrational waves, possibly from the Middle East.

Base Sequence↗
PubMed1996

Genetic and geographical variability in cystic fibrosis: evolutionary considerations.

We have studied cystic fibrosis from an evolutionary perspective by focusing on three main points: the high frequency of cystic fibrosis; the different spectrum of mutations that cause the disease in different areas of Europe; and the age of the delta F508 mutation. Several hypotheses have been suggested to explain the high frequency of cystic fibrosis. We argue that the most plausible is heterozygote resistance to cholera and to other dehydrating intestinal diseases. Different population sizes in the past could explain the higher diversity among cystic fibrosis mutations found in southern Europe. Three microsatellite loci are found close to the delta F508 mutation. The reconstruction of the original microsatellite haplotype in which delta F508 arose, and of the genealogy of the microsatellite haplotypes bearing the mutation, allowed us to date the mutation event at around 50,000 years ago.

Cystic Fibrosis↗
PubMed1996

Identification of a base pair substitution at the tetranucleotide tandem repeat locus DHFRP2 (AAAC)n in a worldwide survey.

An allele heterogeneity in a short tandem repeat at the human dihydrofolate reductase pseudogene (DHFRP2) was detected using non-denaturing gel electrophoresis and ethidium bromide staining. Sequence analysis of the allele, designated 9A, revealed the C to A substitution in the 8th AAAC repeat. A survey of 16 worldwide human populations showed that this mutation was spread through five continents at a relatively high frequency (up to p = 0.19 in Europeans). Some statistical parameters of forensic interest were also calculated (h, PD, EC and PIC) for this polymorphism. This type of heterogeneity stresses the complexity of STR variation.

Alleles↗
PubMed1996

Geographic homogeneity and non-equilibrium patterns of mtDNA sequences in Tuscany, Italy.

The geographical distribution of 49 mtDNA sequences from 22 localities in Southern Tuscany, Italy, was studied by molecular analysis of variance, by a new spatial autocorrelation statistic specifically designed for sequence data and by reconstructing genealogies of haplotypes. All these methods indicated a high homogeneity of populations. Nevertheless, genetic variability showed significant departure from equilibrium expectations, in agreement with the predicted effects of a population expansion. We suggest that a past population expansion that was probably associated with a migrational wave and with local gene flow between localities prevented spatial structuring in Southern Tuscany.

Analysis of Variance↗
PubMed1996

Minisatellite diversity supports a recent African origin for modern humans.

In a study of human diversity at a highly variable locus, we have mapped the internal structures of tandem-repetitive alleles from different populations at the minisatellite MS205 (D16S309). The results give an unusually detailed view of the different allelic structures represented on modern human chromosomes, and of the ancestral relationships between them. There was a clear difference in allelic diversity between African and non-African populations. A restricted set of allele families was found in non-African populations, and formed a subset of the much greater diversity seen on African chromosomes. The data strongly support a recent African origin for modern human diversity at this locus.

Africa↗
PubMed1996

Geographic variation in human mitochondrial DNA control region sequence: the population history of Turkey and its relationship to the European populations.

The hypervariable segment I of the control region of the mtDNA (positions 16024-16383) was amplified from hair roots by PCR and sequenced in 45 unrelated individuals from Anatolia (Asian Turkey). Forty different sequences were found, defined by 56 variable positions, of which only one involves a transversion. The neighbor-joining tree of Kimura's distance matrix for all sequences shows four main clusters. Cluster D was found to be the most statistically robust of the four, and all the sequences in it shared a mutation that is present only in European and West Asian populations. The variability in cluster D could have originated between 37,000 and 107,000 years ago. No branch is unexpectedly long, denoting the absence of sequences that diverged much before the others. The pairwise difference distribution is bell-shaped, in accordance with a population expansion occurring roughly 35,000 to 100,000 years ago. When compared to other Caucasoid populations through the pairwise difference distribution, there is a pattern from the Middle East (older expansion) to the various European populations, with Turkey in an intermediate position; when Turkish sequences are compared through a neighbor-joining tree on a genetic distance matrix of populations, this position is again evidenced. Although there is a very low level of genetic divergence among Caucasoid populations as shown by mtDNA control region sequences, a geographic pattern of genetic variation emerges, denoting a stepping-stone position of Turkey between the Middle East and Europe, which is in agreement with the hypothesis of a replacement of Neanderthals by modern humans, which could be related to the Upper Paleolithic cultural expansion.

Base Sequence↗
PubMed1996

Genetic diversity in the Iberian Peninsula determined from mitochondrial sequence analysis.

We have analysed 302 bp of the first hypervariable region of the mitochondrial D-loop in 271 individuals from different regions of the Iberian Peninsula and 85 individuals from Algeria. The Basque population is significantly different from neighbouring populations in terms of overall levels of diversity. This is because the majority of sequences in the Basques are restricted to the lineage group defined by the CRS (Cambridge Reference Sequence) and its derivatives although, like other Iberian populations, they showed a unimodal distribution of pairwise sequence differences. The timing of divergence of populations within Iberia points to a shared ancestry of all populations in the Upper Palaeolithic. Further genetic subdivision is apparent in Catalonia and Andalusia, with increased genetic diversity in the latter. Lineage diversity comparisons of Iberian populations with European (Tuscan) and North African (Algerian) populations shows the Iberian Peninsula to be more similar to other European populations, although a small number of Iberian lineages can be traced to North Africa.

Algeria↗
PubMed1996

Evidence for a common origin of most Friedreich ataxia chromosomes in the Spanish population.

Haplotype analysis is a powerful approach to understand the spectrum of mutations accounting for a disease in a homogeneous population. We show that haplotype variation for 10 markers linked to the Friedreich ataxia locus (FRDA) argues in favor of an important mutation homogeneity in the Spanish population, and positions the FRDA locus in the region where it has been recently isolated. We also report the finding of a new single nucleotide polymorphism called FAD1. The new marker shows a very strong linkage disequilibrium with Friedreich ataxia (FA) in both the Spanish and French populations. suggesting the existence of an ancient and widespread FRDA mutations. Inclusion of FAD1 in the extended haplotype analysis has allowed to postulate that this main FRDA mutation could account for 50-90% of the disease chromosomes. The results indicate that FA, despite clinical heterogeneity, could have originated from a few initial mutations.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Birth, marriage and death in illegitimacy: a study in northern Portugal.

In populations in which the frequency of illegitimacy is high, illegitimates and legitimates may be subjected to different demographic and social pressures, with social and genetic consequences. A rural population from north-east Portugal is studied and variables from birth, marriage and death records are compared according to the legitimacy of the individuals. The analysis shows important differential demographic patterns in infant and child mortality and in migration prior to and related to marriage, especially in women. Some changes over time and gender differences are also evident.

Age Factors↗
PubMed1995

Heteroplasmy in the control region of human mitochondrial DNA.

The sequencing of a 360-nucleotide segment of the mt DNA control region in a population survey revealed the presence of one individual having heteroplasmy in positions 16,293 (A and G) and 16,311 (C and T). This case indicates that heteroplasmy in humans may not be as rare as generally believed.

Base Sequence↗
PubMed1995

Human mitochondrial DNA variation and the origin of Basques.

The hypervariable segment I of the control region of the mtDNA (positions 16024-16383) was PCR-amplified from mouth scrape and hairs and sequenced in 45 unrelated individuals of pure matrilineal Basque descent. Twenty-seven different sequences were found, of which 21 are unique to the Basques. The allelic partition observed, together with resampling experiments, suggested that much more variation remained to be discovered. The mean pairwise difference in number of nucleotides between individuals was 3-15, a very low value. Moreover, the number of steps for the most parsimonious tree is very low compared to the number of different sequences. Both findings suggest that the Basque population was founded by a few lineages that diverged in a short time span. The number of nucleotide differences between individuals was shown not to be influenced by the distance between their birthplaces, thus validating the sampling strategy used a posteriori. The pairwise difference distribution agreed well with the three-parameter model proposed by Rogers & Harpending (1992). The parameter estimates found for the Basques implied that a demographic expansion (or perhaps two, given the bimodal shape of the distribution) took place sometime between 14500 and 42000 BP which is in agreement with archaeological data. Our sample was compared to other populations for which D-loop sequences were available through the Nei & Miller (1990) distance. In a neighbour-joining tree, all the Caucasoid samples, including the Basques, appeared tightly clustered, whereas African samples were the most distant to the Caucasoids and also the most heterogeneous. Although classical markers, such as blood groups and protein polymorphisms, clearly separate the Basques (and the Sardinians) from other European populations, this distinctiveness was not found using D-loop sequences.

Base Sequence↗
PubMed1995

Reproductive rates in families of schizophrenic patients in a case-control study.

Data about the fertility of 142 schizophrenic patients and their ancestors are reported and compared with healthy people in a case-control study. The biological fitness of the patients is 76% of controls in individuals with at least one child, and 48% of controls in all patients, with clear low fertility rates in patients, especially in men. When looking at the previous generations, the existence of a significant increase in fertility in the relatives of schizophrenics was reinforced in the maternal lineage. These results confirm the previous findings about the decreasing fertility in schizophrenic patients and may be of interest in understanding the maintenance of the illness despite its genetic background.

Adolescent↗
PubMed1995

Do Basque- and Caucasian-speaking populations share non-Indo-European ancestors?

Genetic evidence is consistent with the view that the Indo-European languages were propagated in Europe by the diffusion of early farmers. The existence of phylogenetic relationships between European populations speaking other languages has been proposed on linguistic and archaeological grounds, and is here tested by analyzing allele frequencies at ten polymorphic protein and blood group loci. Genetic distances between speakers of Basque and Caucasian languages are compared with those between controls, i.e. contiguous populations speaking Indo-European and Altaic. Although some statistical tests show an excess of genetic similarity between Basque and South Caucasian speakers, most results do not support their common origin. If the Basques and the Caucasian-speaking populations share common ancestors, recent evolutionary phenomena must have caused divergence between them, so that their gene frequencies do not appear more similar now than those of random pairs of populations separated by the same geographic distance.

Biological Evolution↗
PubMed1994

Principal component analysis of gene frequencies and the origin of Basques.

The genetic peculiarity of the Basque population has long been noted. We aim to describe Basque distinctiveness in space and assess the internal Basque heterogeneity. All these aspects are relevant to the question of the origin of Basques. After a thorough literature search, a data base was created containing all the available data on gene frequencies in the Iberian Peninsula and France. Twenty-nine systems, comprising 71 alleles, were used to carry out a principal component (PC) analysis. The results show a sharp peak in the first PC in the Basque area, which remains even when the geographic scope is widened to include western Europe. As demonstrated by "wombling" analysis, the steeper slope in the first PC is found to the east of the Basque area, along the Pyrenees. Measures of genetic heterogeneity (such as FST values) within the Basque country, as compared to those for non-Basques, do not show a particular internal substructuration in the Basque population. The genetic results support a scenario in which the Basques are the product of in situ differentiation around the time of the Last Glacial Maximum (18,000 B.P.), in agreement with archaeological and linguistic data. Isolation from the surrounding populations has allowed the differentiation to last for millennia, but has erased the differences existing among Basques.

Alleles↗
PubMed1994

The origin of the major cystic fibrosis mutation (delta F508) in European populations.

delta F508 is the most frequent cystic fibrosis (CF) mutation and accounts for approximately 70% of CF chromosomes worldwide. Three highly polymorphic microsatellite markers have been used to study the origin and evolution of delta F508 chromosomes in Europe. Haplotype data demonstrate that delta F508 occurred more than 52,000 years ago, in a population genetically distinct from any present European group, and spread throughout Europe in chronologically distinct expansions, which are responsible for the different frequencies of delta F508 in Europe.

Biological Evolution↗
PubMed1994

Mountains and genes: population history of the Pyrenees.

The Pyrenees Mountains rise between France and Spain. At their western end live the Basques, one of the oldest populations in Europe. All the available genetic information (gene frequencies of blood groups, serum proteins, red cell enzymes, and HLA antigens) on Pyrenean populations has been gathered and subjected to two kinds of analysis: a discrete approach, in which eight separate populations have been defined according to linguistic and geographic criteria to compute genetic distances between them; and a continuous principal components analysis on gene frequencies interpolated to a regular grid. In the first approach the Pyrenean samples have also been compared to other Western European populations. Our results show that the Basque population is most genetically differentiated with respect to other Pyrenean and Western European populations. There is a strong genetic gradient along the mountain range (i.e., in an east-west direction); thus the mountains have not acted as barriers to gene flow. A Catalan-speaking sample, the Cerdanya, is slightly detached from its neighbors and seems closer to other European populations. This genetic picture together with linguistic, paleoanthropological, and archeological data points to a Mesolithic (or older) differentiation of the Cantabrian ancestors of the Basques. Moreover, the Basque genetic features are found in the northern slope of the Pyrenees far beyond the present Basque linguistic boundaries, in accordance with the most recent hypotheses on Pyrenean historical linguistics. The genetic consequences of the arrival of the first Indo-European-speaking peoples in the Iberian Peninsula are also studied; no clear genetic trace has been left of that population movement, except perhaps for the Cerdanya, an eastern valley that affords a passage between north and south.

Algorithms↗