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PubMed2005

[Allozyme polymorphism of Swiss stone pine Pinus cembra L. in mountainous populations of the Alps and the Eastern Carpathians].

Swiss stone pine Pinus cembra L. is a species with fragmented range, occurring in the Alpine-East Carpathian mountain system. Seeds of P. cembra are dispersed by nutcrackers, which offers potential possibilities for gene exchange among populations. Using isozyme analysis, we have examined five samples from two parts of the Swiss stone pine range: the Alps (Switzerland and Austria) and the Carpathians (two samples from the northern macroslope of the Gorgany Ridge, Eastern Carpathians, Ivano-Frankovsk oblast and one sample from Trans-Carpathian oblast of Ukraine). The allele frequencies of 30 isozyme loci, coding for enzymes ADH, FDH, FEST, GDH, GOT, IDH, LAP, MNR, MDH, PEPCA, 6PGD, PGI, PGM, SDH, SKDH, SOD, were analyzed using cluster analysis and methods of principal components. Two clusters, corresponding to the isolated Alpine and Carpathian parts of the range, were found. The main contribution to these differences were made by loci Adh-1, Adh-2, Fest-2, Lap-3, Mdh-4, and Sod-4. The interpopulation differentiation proved to be somewhat higher than that typical for pines (F(ST) = 7.4%), but within the limits characteristic for taxonomically close species. Thus, isolation of the populations did not lead to their marked differentiation, which may be explained by gene flow and balancing selection, which equalizes gene frequencies across the fragmented species area. Interlocus F(ST) heterogeneity (from 0.003 to 0.173) suggests adaptive significance of some of the allozyme polymorphisms or linkage of some loci with adaptive genes. The Carpathian populations were shown to have higher gene diversity than the Alpine ones (expected heterozygosities 0.095-0.114 and 0.060-0.080, respectively). A deficit of heterozygotes (as compared to the Hardy-Weinberg proportions), observed in the embryo sample, was probably explained by inbreeding. The reduction in the area of Carpathian pine forests in Holocene, caused by the global climatic changes and the anthropogenic impact, is hazardous for the gene pool of the species. The maintenance of genetic uniqueness of both Carpathian populations of P. cembra in general, and individual stands in particular, requires special measures for protection of Swiss stone pine in the Eastern Carpathians.

Environment↗
PubMed1985

T-cell receptor beta-chain expression: dependence on relatively few variable region genes.

Fifteen independently isolated complementary DNA clones that contain T-cell receptor (TCR) V beta genes were sequenced and found to represent 11 different V beta genes. When compared with known sequences, 14 different V beta genes could be defined from a total of 25 complementary DNA's; 11 clones therefore involved repeated usage of previously identified V beta's. Based on these data, we calculate a maximum likelihood estimate of the number of expressed germline V beta genes to be 18 with an upper 95 percent confidence bound of 30 genes. Southern blot analysis has shown that most of these genes belong to single element subfamilies which show very limited interstrain polymorphism. The TCR beta-chain diversity appears to be generated from a limited V beta gene pool primarily by extensive variability at the variable-diversity-joining (V-D-J) junctional site, with no evidence for the involvement of somatic hypermutation.

Alleles↗
PubMed2000

High frequency of alkaptonuria in Slovakia: evidence for the appearance of multiple mutations in HGO involving different mutational hot spots.

Alkaptonuria (AKU) is an autosomal recessive disorder caused by the deficiency of homogentisate 1,2 dioxygenase (HGO) activity. AKU shows a very low prevalence (1:100,000-250,000) in most ethnic groups. One notable exception is in Slovakia, where the incidence of AKU rises to 1:19,000. This high incidence is difficult to explain by a classical founder effect, because as many as 10 different AKU mutations have been identified in this relatively small country. We have determined the allelic associations of 11 HGO intragenic polymorphisms for 44 AKU chromosomes from 20 Slovak pedigrees. These data were compared to the HGO haplotype data available in our laboratory for >80 AKU chromosomes from different European and non-European countries. The results show that common European AKU chromosomes have had only a marginal contribution to the Slovak AKU gene pool. Six of the ten Slovak AKU mutations, including the prevalent G152fs, G161R, G270R, and P370fs mutations, most likely originated in Slovakia. Data available for 17 Slovak AKU pedigrees indicate that most of the AKU chromosomes have their origins in a single very small region in the Carpathian mountains, in the northwestern part of the country. Since all six Slovak AKU mutations are associated with HGO mutational hot spots, we suggest that an increased mutation rate at the HGO gene is responsible for the clustering of AKU mutations in such a small geographical region.

Alkaptonuria↗
PubMed1996

The genetical archaeology of the human genome.

Palaentology and archaeology are disciplines that traditionally deal with the reconstruction of human origins and history. Recently, however, molecular genetics has come to make increasing contributions to this area. In particular, several data sets indicate that variation of the human gene pool originated in Africa within the last 200,000 years. Furthermore, the study of DNA sequences allows the detection of expansions in population size. Here we briefly summarize and exemplify how DNA sequences can be used to reconstruct the history of populations.

DNA, Mitochondrial↗
PubMed2000

HLA polymorphism and evaluation of European, African, and Amerindian contribution to the white and mulatto populations from Paraná, Brazil.

Polymorphism of classical HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ genes differs greatly among populations, both in frequencies and in the presence of alleles and haplotypes particular to population groups, making these genes powerful tools for the study of origins of populations and their degree of admixture. Antigen, allele, and haplotype frequencies, together with linkage disequilibrium patterns, are reported for 2 populations in the southern Brazilian state of Paraná, one of predominantly European ancestry (white), the other of predominantly African and European ancestry (mulatto). Genetic distance estimates between the 2 groups and other populations studied previously, and of degree of admixture, were performed. In accordance with phenotypic classification, the white population is of predominantly European origin (80.6%), with a smaller contribution of African (12.5%) and Amerindian (7.0%) genes. The mulatto population consists of African (49.5%) and European (41.8%) ancestry, with a smaller but significant contribution of Amerindian (8.7%) ancestry. On the basis of history and population genetics, there is controversy regarding the Amerindian contribution to Paraná's gene pool. These results provide a better picture of Paraná's ethnic constitution and on the Amerindian contribution to the white and mulatto populations.

Adult↗
PubMed2000

Multiple origins of Tibetan Y chromosomes.

The genetic origin of Tibetans was investigated using Y chromosome markers. A total of three populations were studied, two from central Tibet speaking central Tibetan and one from Yunnan speaking Kham. Two dominant paternal lineages (>80%) were identified in all three populations with one possibly from central Asia (YAP+) and the other from east Asia (M122C). We conclude that Tibetan Y chromosomes may have been derived from two different gene pools, given the virtual absence of M122C in central Asia and YAP+ in east Asia, with drift an unlikely mechanism accounting for these observations.

Alu Elements↗
PubMed2002

Greater genetic variability in Argentine Creole than in Thoroughbred horses based on serum protein polymorphisms.

Genetic polymorphism was analyzed for five blood proteins: albumin - Al, esterase - Es, alpha(1)B-glycoprotein - Xk, transferrin - Tf and hemoglobin - Hb in 200 Thoroughbred (TB) and 124 Argentine Creole (AC) horses. Of the five systems examined, Tf and Hb were not in Hardy-Weinberg equilibrium in either breed and Es was not in equilibrium in the Creole breed. Genetic variability, estimated as average heterozygosity, was higher in AC (H = 0.585 +/- 0.131) than in TB (H = 0.353 +/- 0.065). The genetic differentiation between these two populations (F(ST)) was 0.109. Thus, of the total genetic differences between breeds, the proportion of genetic variation attributable to breed differences was about 10%; the remaining 90% was due to individual variation within breeds. The high degree of genetic variability seen in Argentine Creole horses could be a consequence of natural selection. Selection of TB through the centuries has most likely modified the gene pool of the ancestral population, with a consequent reduction in variability at certain loci. Probably, different mechanisms exist for maintaining polymorphism at these loci in TB and in AC horses. Heterozygosity may have played a fundamental role in adaptation.

Animals↗
PubMed2005

Africanization in the United States: replacement of feral European honeybees (Apis mellifera L.) by an African hybrid swarm.

The expansion of Africanized honeybees from South America to the southwestern United States in <50 years is considered one of the most spectacular biological invasions yet documented. In the American tropics, it has been shown that during their expansion Africanized honeybees have low levels of introgressed alleles from resident European populations. In the United States, it has been speculated, but not shown, that Africanized honeybees would hybridize extensively with European honeybees. Here we report a continuous 11-year study investigating temporal changes in the genetic structure of a feral population from the southern United States undergoing Africanization. Our microsatellite data showed that (1) the process of Africanization involved both maternal and paternal bidirectional gene flow between European and Africanized honeybees and (2) the panmitic European population was replaced by panmitic mixtures of A. m. scutellata and European genes within 5 years after Africanization. The post-Africanization gene pool (1998-2001) was composed of a diverse array of recombinant classes with a substantial European genetic contribution (mean 25-37%). Therefore, the resulting feral honeybee population of south Texas was best viewed as a hybrid swarm.

Africa↗
PubMedDate not supplied

Some genetic considerations for the design of better mammalian assay systems for the detection of chemical mutagens and carcinogens.

Fuller utilization of the potential for genetic manipulation of the laboratory animal populations producing test animals should aid in the development of more sensitive, relevant, and economic toxicologic assay systems for the generation of dose response data at environmental exposure levels. One example of such genetic manipulation is the incorporation, in laboratory mouse populations of any desired genetic structure, of dominant visible mutations which enhance tumor formation. Thus, two different levels of inherent susceptibility to tumor formation can be incorporated and visually identified in the same test population. Another example is the manipulation of the genetic structure of a laboratory animal population in order to generate F-1 hybrids, hybrid crosses, or minimally inbred stocks from the same gene pool. Which of these genetic structures is most suitable in any particular case depends on the purpose for which the assay data are to be used. In making a choice, the desired degree of genetic heterogeneity of the population and the phenotypic variability of the toxicologic responses to be assayed must be considered.

Animals↗
PubMed2000

Jewish and Middle Eastern non-Jewish populations share a common pool of Y-chromosome biallelic haplotypes.

Haplotypes constructed from Y-chromosome markers were used to trace the paternal origins of the Jewish Diaspora. A set of 18 biallelic polymorphisms was genotyped in 1,371 males from 29 populations, including 7 Jewish (Ashkenazi, Roman, North African, Kurdish, Near Eastern, Yemenite, and Ethiopian) and 16 non-Jewish groups from similar geographic locations. The Jewish populations were characterized by a diverse set of 13 haplotypes that were also present in non-Jewish populations from Africa, Asia, and Europe. A series of analyses was performed to address whether modern Jewish Y-chromosome diversity derives mainly from a common Middle Eastern source population or from admixture with neighboring non-Jewish populations during and after the Diaspora. Despite their long-term residence in different countries and isolation from one another, most Jewish populations were not significantly different from one another at the genetic level. Admixture estimates suggested low levels of European Y-chromosome gene flow into Ashkenazi and Roman Jewish communities. A multidimensional scaling plot placed six of the seven Jewish populations in a relatively tight cluster that was interspersed with Middle Eastern non-Jewish populations, including Palestinians and Syrians. Pairwise differentiation tests further indicated that these Jewish and Middle Eastern non-Jewish populations were not statistically different. The results support the hypothesis that the paternal gene pools of Jewish communities from Europe, North Africa, and the Middle East descended from a common Middle Eastern ancestral population, and suggest that most Jewish communities have remained relatively isolated from neighboring non-Jewish communities during and after the Diaspora.

Base Sequence↗
PubMed1999

Genetic population structure of two African-Ecuadorian communities of Esmeraldas.

The genetic structure of two African-Ecuadorian communities, Rio Cayapas and Viche (Esmeraldas province, northwest Ecuador), was studied on the basis of ACP1, ADA, AK1, CA2, ESD, GLO1, G6PD, PGD, and PGM1 subtypes and thermostability, PGM2, HBbeta, F13A, F13B, ORM1, AHSG, C6, C7, and APOC2 gene frequency, and migration data on 255 individuals. The fixation index of Wright (F(ST)), correspondence, and genetic distance analysis were applied to compare the genetic relationships between these communities and other American populations of African ancestry. F(ST) values from the migration data and surname origins suggest that Rio Cayapas is genetically more isolated and shows less mobility and admixture than does Viche. The genetic admixture estimates indicate a large contribution of African genes to the gene pool of both communities (74.3% to 58.4%), whereas the proportion of the Amerindian component differs significantly (14.5% in Rio Cayapas to 27.6% in Viche).

Africa↗
PubMedDate not supplied

On germ plasm conservation with special reference to the genus Medicago.

As Frankel has indicated, there is ample justification for maintaining international germ plasm centers for preservation of land races and species of a genus; this would appear self-evident on the grounds that extinction involves a permanent loss of gene pools that have required from several centuries to millions of years to evolve. Monoculture is causing extinction of some Medicago species, yet all species of the genus Medicago are of economic importance. Examples are drawn from recent crosses involving wild species of this genus, and we note the rapidly increasing appreciation of the value of annual Medicago species. Their potential future use in the South Temperate Zone countries is discussed.

Cost-Benefit Analysis↗
PubMed2003

Craniometric evidence for Palaeoamerican survival in Baja California.

A current issue on the settlement of the Americas refers to the lack of morphological affinities between early Holocene human remains (Palaeoamericans) and modern Amerindian groups, as well as the degree of contribution of the former to the gene pool of the latter. A different origin for Palaeoamericans and Amerindians is invoked to explain such a phenomenon. Under this hypothesis, the origin of Palaeoamericans must be traced back to a common ancestor for Palaeoamericans and Australians, which departed from somewhere in southern Asia and arrived in the Australian continent and the Americas around 40,000 and 12,000 years before present, respectively. Most modern Amerindians are believed to be part of a second, morphologically differentiated migration. Here we present evidence of a modern Amerindian group from the Baja California Peninsula in Mexico, showing clearer affinities with Palaeoamerican remains than with modern Amerindians. Climatic changes during the Middle Holocene probably generated the conditions for isolation from the continent, restricting the gene flow of the original group with northern populations, which resulted in the temporal continuity of the Palaeoamerican morphological pattern to the present.

Adaptation, Biological↗
PubMedDate not supplied

Exotic mice as models for aging research: polemic and prospectus by R. Miller et al.

Miller and colleagues present a polemic against uniform genotypes in gerontological research and a paean for genetically heterogeneous populations. Both on simple sampling considerations, and because of selective loss of alleles through inbreeding depression, inbred strains are idiosyncratic, and the lack of genetic variance within strains limits their utility in examining relationships among phenotypes. Heterogeneous stocks, by contrast, are not impaired by inbreeding depression, and the presence of genetic and environmental variance provides for effective assessment of correlations among variables. Those assembled by intermating of inbred strains are replicable in terms of gene pool parameters, even if no individual can ever be replicated, and those derived from wild-trapping may include alleles absent for whatever reason from current laboratory strains. This author concurs that there are limitations on research with uniform genotypes and advantages of heterogeneous populations. However, for specific purposes, the uniformity and stability of inbred strains are extremely valuable attributes, and heterogeneous stocks have their own limitations. Researchers should select the animal model most appropriate for their specific purpose.

Aging↗
PubMed1998

Study of 15 protein polymorphisms in a sample of the Turkish population.

Anatolia, because of its geographic position and its use as an area of settlement, was also a land of transit that accommodated a succession of populations. The last important invasion occurred in the Middle Ages with the arrival of the Turks, an Altaic-speaking nomadic population descended from the Oguz tribes and originating in Mongolia. Although the Turks imposed their culture, their genetic contribution seems to have been modest. To validate this hypothesis, we studied the genetic structure of the Turkish population by examining 15 genetic markers in a sample of 93 subjects. The allele frequencies observed were HP*1 = 0.240; GLO1*1 = 0.344, ESD*2 = 0.134, GC*1S = 0.613, GC*1F = 0.129, PGM1*2S = 0.322, PGM1*2F = 0.041, PGM1*1F = 0.027, F13B*1 = 0.762, F13B*2 = 0.101, ORM1*S = 0.327, AHSG*2 = 0.181, C6*B = 0.239, C7*1 = 0.983, APOC2*1 = 1.0, APOE*3 = 0.868, APOE*2 = 0.063, BF*F = 0.258, BF*S07 = 0.017, BF*SQ0 = 0.011, C4A*Q0 = 0.145, C4A*2 = 0.070, C4A*5 = 0.012, C4A*6 = 0.023, C4B*Q0 = 0.101, C4B*2 = 0.048, C4B*3 = 0.005, and C4B*11 = 0.005. The present Turkish population was compared to other European, Middle Eastern, and North African populations by means of correspondence analysis. Turks cluster with Turkomans, who share the ancient Turks' derivation from the Oguz tribe. Moreover, Turks clearly belong to European groups and resemble the populations of neighboring countries. Therefore the present data support the hypothesis that the ancient Turkish tribes, who started to enter Anatolia 1000 years ago, contributed little to the gene pool of the preexisting Anatolian populations. Alternatively, if the genetic structure of the invading Turks resembled that of the ancient Anatolians, it will be impossible to find traces of their admixture with the autochthonous inhabitants of Anatolia. However, further analysis of other samples from Turkey and from populations living in the homelands of the Turkish tribes, namely, the eastern area of the Caspian Sea and Mongolia, is needed.

Adult↗
PubMed2000

The genetic legacy of Paleolithic Homo sapiens sapiens in extant Europeans: a Y chromosome perspective.

A genetic perspective of human history in Europe was derived from 22 binary markers of the nonrecombining Y chromosome (NRY). Ten lineages account for >95% of the 1007 European Y chromosomes studied. Geographic distribution and age estimates of alleles are compatible with two Paleolithic and one Neolithic migratory episode that have contributed to the modern European gene pool. A significant correlation between the NRY haplotype data and principal components based on 95 protein markers was observed, indicating the effectiveness of NRY binary polymorphisms in the characterization of human population composition and history.

Alleles↗
PubMed1999

Deletion polymorphism in the human COL1A2 gene: genetic evidence of a non-African population whose descendants spread to all continents.

We report the frequencies of a deletion polymorphism at the alpha 2 (1) collagen gene (COL1A2) and argue that this distribution has major implications for understanding the evolution of modern humans immediately after their exodus from sub-Saharan Africa as well as their subsequent spread to all continents. The high frequency of the deletion in non-African populations and its complete absence in sub-Saharan African groups suggest that the deletion event occurred just before or shortly after modern humans left Africa. The deletion probably arose shortly after the African exodus in a group whose descendants were among the ancestors of all contemporary populations, except for sub-Saharan Africans. This, of course, does not imply that there was a single migration out of Africa. The GM immunoglobulin haplotype GM*A,X G displays a similar distribution to that for the COL1A2 deletion, and these 2 polymorphisms suggest that the exodus from Africa may not have been a rapid dispersion to all other regions of the world. Instead, it may have involved a period of time for the savanna-derived gene pool to adapt to novel selective agents, such as bacteria, viruses, and/or environmental xenobiotics found in both animal and plant foods in their new environment. In this context these polymorphisms are indicators of the evolution that occurred before the diaspora of these populations to the current distribution of modern peoples.

Africa South of the Sahara↗
PubMed2004

The origin of the isolated population of the Faroe Islands investigated using Y chromosomal markers.

Historical, archaeological and linguistic sources suggest that the ancestors of the present day population in the Faroe Islands may have their origin in several different regions surrounding the North Atlantic Ocean. In this study we use binary and microsatellite markers of the Y chromosome to analyse genetic diversity in the Faroese population and to compare this with the distribution of genotypes in the putative ancestral populations. Using a combination of genetic distance measures, assignment and phylogenetic analyses, we find a high degree of similarity between the Faroese Y chromosomes and the Norwegian, Swedish and Icelandic Y chromosomes but also some similarity with the Scottish and Irish Y chromosomes. Diversity measures and estimates of effective population sizes also suggest that the original gene pool of the settlers have been influenced by random genetic drift, thus complicating direct comparisons with other populations. No extensive immigration from Iceland to the Faroe Islands can be documented in the historical record. We therefore hypothesise that the high degree of Y chromosome similarity between the two populations arose because they were colonised at approximately the same time by males originating from the same regions of Scandinavia and, to a lesser extent, from the British Isles.

Atlantic Islands↗