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At least 1,027 records · Page 57Linked to original sources
PubMed1989

The genetic structure of populations of Chuckotka Peninsula Eskimos and Chuckchi based on study of 13 loci of serum and erythrocyte proteins and enzymes.

The Eskimos and Chuckchi of the Chuckotka Peninsula were studied at 13 loci of serum and erythrocyte proteins and enzymes by electrophoresis. Six loci-including albumin, transferrin, carbonic anhydrase I and II, monoamine oxidase, and superoxide dismutase-were monomorphic in the studied populations. The mean frequencies of alleles in nine polymorphic loci of Chuckotka Eskimos and Chuckchi, Eskimos of Alaska, Canada, and Greenland, some Mongoloid populations of Siberia, American Indians, and Lapps of circumpolar areas of Western Europe were obtained. The genetic distances between these populations were calculated. The Eskimos of Chuckotka were closest to the Alaskan Eskimos. The relative heterozygosity of Chuckotka Eskimos was calculated and was the highest in Chuckchi. The average heterozygosity in Eskimo populations increased in the following order, from least to greatest: Chuckotka Eskimos, St. Lawrence Island Eskimos, Alaskan Eskimos, Greenland Eskimos, and Canadian Eskimos. The average heterozygosity of the Chuckchi was similar to that of Western Hemisphere Eskimos.

Alaska↗
PubMed1997

Geographical genetic structure within the human lung fluke, Paragonimus westermani, detected from DNA sequences.

Nucleotide sequences were obtained for the second internal transcribed spacer of the ribosomal gene repeat and for part of the mitochondrial-cytochrome c oxidase subunit I gene from geographical isolates of Paragonimus westermani from Japan, China, Korea, Taiwan, the Philippines, peninsular Malaysia and Thailand. Sequences were obtained from several other species of Paragonimus for comparative purposes. Two groups were recognized within P. westermani: an NE group (China, Japan, Korea, Taiwan) which was relatively uniform and included both diploid and triploid forms, and a southern group (Malaysia, Thailand, Philippines), members of which were genetically distant from one another. According to both ITS2 and COI data, genetic distances among P. westermani isolates equalled or exceeded those between some distinct species of Paragonimus. The ITS2 sequences were conserved relative to COI sequences. Substitutions among the latter may be approaching saturation within the genus Paragonimus.

Animals↗
PubMed2000

Phylogeography and genetic structure of northern populations of the yellow warbler (Dendroica petechia).

Phylogeographic patterns of intraspecific variation can provide insights into the population-level processes responsible for speciation and yield information useful for conservation purposes. To examine phylogeography and population structure in a migratory passerine bird at both continental and regional geographical scales, we analysed 344 bp of mitochondrial DNA (mtDNA) control region sequence from 155 yellow warblers (Dendroica petechia) collected from seven locations across Canada and from Alaska. There is a major subdivision between eastern (Manitoba to Newfoundland) and western (Alaska and British Columbia) populations which appears to have developed during the recent Pleistocene. Some localities within these two regions also differ significantly in their genetic composition, suggesting further subdivision on a regional geographical scale. Eastern and western birds form distinct phylogeographic entities and the clustering of all western haplotypes with two eastern haplotypes suggests that the western haplotypes may be derived from an eastern lineage. Analyses based on coalescent models support this explanation for the origin of western haplotypes. These results are consistent with important features of Mengel's model of warbler diversification. From a conservation perspective they also suggest that individual populations of migrant birds may form demographically isolated management units on a smaller scale than previously appreciated.

Alaska↗
PubMed1976

Genetic structure of a tribal population, the Yanomama Indians. XIII. Dental microdifferentiation.

Data are presented on the frequency of the following eight dental traits in 635 Yanomama and 65 Makiritare Indians: upper central incisor rotation or winging, shoveling of maxillary incisors, maxillary molar hypocone reduction, Carabelli's trait, mandibular molar cusp number, mandibular molar cusp pattern rotation of second lower premolar, and pattern of second lower premolar cusps. Yanomama dentition is unusual in the high frequency of six cusps on the mandibular molars. There is marked dental microdifferentiation between villages; significant agreement was observed between a matrix of pairwise "dental distances" based on six morphological traits and corresponding matrices based on 11 genetic systems and on geographic location.

Brazil↗
PubMed2000

Genetic structure of north-west Africa revealed by STR analysis.

We have analysed a large set of autosomal short tandem repeat (STR) loci in several Arabic and Berber-speaking groups from north-west Africa (ie Moroccan Arabs, northern-central and southern Moroccan Berbers, Saharawis, and Mozabites). Two levels of analysis have been devised using two sets of 12STR loci, (D3S1358, vWA, FGA, THO1, TPOX, CSF1PO, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820) and 21 (the former set plus D9S926, D11S2010, D13S767, D14S306, D18S848, D2S1328, D4S243, F13A1, and FES/FPS). For each set, data for a number of external reference populations were gathered from the literature. Several methods of analysis based on genetic distances (neighbour-joining trees, principal coordinate analysis, boundary detection), as well as AMOVA, showed that genetic differentiation among NW African populations was very low and devoid of any spatial pattern. When the NW African populations were grouped according to cultural or linguistic differences, the partition was not associated with genetic differentiation. Thus, it is likely that Arabisation was mainly a cultural process. A clear genetic difference was found between NW African populations and Iberians, which underscores the Gilbraltar Straits as a strong barrier to genetic exchange; nonetheless, some degree of gene flow into Southern Iberia may have existed. NW Africans were genetically closer to Iberians and to other Europeans than to African Americans.

Africa, Northern↗
PubMed2006

Genetic structure among 38 populations from the United States based on 11 U.S. core Y chromosome STRs.

A DNA database consisting of the 11 Y chromosome short-tandem-repeat (Y-STR) recommended by the Scientific Working Group on DNA Analysis Methods is constructed for 2517 individuals from 38 populations in the United States. The population samples derive from five ethnic groups currently living in 10 states. A multidimensional scaling (MDS) plot places the populations into four discrete clusters (African Americans (AA), European Americans (EA), Hispanic Americans (HA), and Asian Americans (SA)) and one dispersed cluster of Native Americans. An analysis of molecular variance (AMOVA) indicates that a large proportion of the total genetic variance is partitioned among ethnic groups (24.8%), whereas only a small amount (1.5%) is found among-populations within ethnic groups. Separate AMOVA analyses within each ethnic group show that only the NA sample contains statistically significant among-population variation. Pair wise population differentiation tests do uncover heterogeneity among EA and among HA populations; however, this is due to only a single sample within each group. The analyses support the creation of AA, EA, HA, and Asian American databases in which samples from different geographic regions within the United States are pooled. We recommend that separate databases be constructed for different NA groups.

Analysis of Variance↗
PubMed1988

An analysis of the response of recombinant congenic lines of chickens to RSV challenge provides evidence for further complexity of the genetic structure of the chicken MHC (B).

We found that CB (B12/B12) and CB.R1 (B12r1/B12r1) congenic chicken lines differing from each other only in the B-G region of the MHC(B), although both of them could be characterized as regressors of Rous sarcomas induced by PR-C and BH-C, are distinguishable in their response to the challenge with these two viruses by means of some parameters of tumour growth. This points further to the concept of functional and structural complexity of the B-G region. Both CB and CB.R1 lines are highly susceptible to progressive growth of sarcomas induced by BH-D virus. This suggests a crucial role of helper viruses of different antigenic subgroups used for complementation of the Bryan high-titre pseudotype (BH) of RSV in the pathogenesis of tumours in this experimental system. Furthermore, attempts were made to analyse both primary and secondary response to the challenge with different strains of RSV in the genetic model encompassing the Prague congenic lines CB (B12/B12), CC (B4/B4), CB.R1 (B12r1/B12r1), CC.R1 (B4r1/B4r1) and their F1 hybrids, and a number of backcross matings. The data led to the view that interacting genes within both B-F/L and B-G regions of the MHC(B) govern the observed hierarchy of the response to RSV challenge.

Animals↗
PubMedDate not supplied

[Genetic structure, variability and differentiation of Pinus sylvestris L. populations in the Ukrainian Carpathian Mountains and Rastoch'e].

On the basis of electrophoretic analysis of 9 enzymous systems encoded by 20 gene loci the level of intra- and inter-population variation of two relict populations of Pinus sylvestris L. in the Ukrainian Carpathians and two ones in Rastochiye was studied. The less allele representation and the lower level of heterozygosity are typical for the Carpathian populations. Fst and Gst, parameters of populations subdivision, were not high--0.020 and 0.022 correspondingly and the coefficient DN was 0.008 in average. The results of the cluster analysis showed that only the populations of Rastochiye were united in one group indicating their genetic affinity.

Alleles↗
PubMed2004

[Genetic structure of people from the Volga-Ural region and Central Asia from data of Alu-polymorphism].

Nine Alu loci (Ya5NBC5, Ya5NBC27, Ya5NBC148, Ya5NBC182, YA5NBC361, ACE, ApoA1, PV92, TPA25) were analyzed in six ethnic populations (Trans-Ural Bashkirs, Tatars-Mishars, Mordovians-Moksha, Mountain Maris, Udmurts, and Komi-Permyaks) of the Volga-Ural region and in three Central Asian populations (Uzbeks, Kazakhs, and Uigurs). All Alu insertions analyzed appeared to be polymorphic in all populations examined. The frequency of insertion varied from 0.110 in Mountain Maris at the Ya5NBC5 locus to 0.914 in Tatars at the ApoA1 locus. The data on the allele frequency distribution at nine loci point to the existence of substantial genetic diversity in the populations examined. The value of the observed heterozygosity averaged over nine Alu insertions varied from 0.326 in Mountain Maris to 0.445 in Kazakhs and Uigurs. The level of the interpopulation genetic differences for the Volga-Ural population (Fst = 0.061) was higher than for the populations of Central Asia (Fst = 0.024), Europe (Fst = 0.02), and Southeastern Asia (Fst = 0.018). The populations examined were highly differentiated both in respect of linguistic characteristics and the geographical position. The data obtained confirmed the effectiveness of the marker system used for the assessment of genetic differentiation and the relationships between the ethnic groups.

Alu Elements↗
PubMed2004

Populational genetic structure of free-living maned wolves (Chrysocyon brachyurus) determined by proteic markers.

Electrophoretic analysis of presumptive twenty gene loci products was conducted in hemolisates and plasma samples of twenty-eight maned wolves (Chrysocyon brachyurus) from an area in northeastern São Paulo State, Brazil. The area sampled was divided into three sub-areas, with the Mogi-Guaçu and Pardo rivers regarded as barriers to the gene flow. The polymorphism degree and heterozygosity level (intralocus and average) estimated in this study were similar to those detected by other authors for maned wolves and other species of wild free-living canids. The samples of each sub-area and the total sample exhibited genotype frequencies consistent with the genetic equilibrium model. The values of the F-statistics evidenced absence of inbreeding and population subdivision and, consequently, low genetic distances were found among the samples of each area.

Animals↗
PubMed2007

From social to genetic structures in central Asia.

Pastoral and farmer populations, who have coexisted in Central Asia since the fourth millennium B.C., present not only different lifestyles and means of subsistence but also various types of social organization. Pastoral populations are organized into so-called descent groups (tribes, clans, and lineages) and practice exogamous marriages (a man chooses a bride in a different lineage or clan). In Central Asia, these descent groups are patrilineal: The children are systematically affiliated with the descent groups of the father. By contrast, farmer populations are organized into families (extended or nuclear) and often establish endogamous marriages with cousins. This study aims at better understanding the impact of these differences in lifestyle and social organization on the shaping of genetic diversity. We show that pastoral populations exhibit a substantial loss of Y chromosome diversity in comparison to farmers but that no such a difference is observed at the mitochondrial-DNA level. Our analyses indicate that the dynamics of patrilineal descent groups, which implies different male and female sociodemographic histories, is responsible for these sexually-asymmetric genetic patterns. This molecular signature of the pastoral social organization disappears over a few centuries only after conversion to an agricultural way of life.

Agriculture↗
PubMed1989

Genetic structure, function and regulation of the transposable element IS21.

The IncP plasmid R68.45 and other plasmids carrying tandem repeats of the insertion sequence IS21 [= (IS21)2] produce replicon fusions via transposition at high frequencies in Escherichia coli and other gram-negative bacteria, whereas plasmids with a single IS21 copy, e.g. R68, give replicon fusions rarely. The 2131 bp nucleotide sequence of IS21 was determined; at the ends there were 11 bp inverted repeats with one mismatch. Two adjacent open reading frames, istA and istB, were located on one DNA strand of IS21. In E. coli maxicells, polypeptides of 46 kDa (the istA gene product) and 30 kDa (the istB gene product) were expressed by (IS21)2 plasmids, but not by IS21 plasmids. Genetic analysis of (IS21)2 plasmids indicates that the IS21-IS21 junctions form a promoter, which initiates transcription of the istAB operon in one of the two IS21 elements. A single IS21 element fused to an inducible external tac promoter expressed both proteins after induction, but did not promote effective replicon fusion, unless an IS21-IS21 junction (the preferred site for IS21 transposase action) was also present on the plasmid carrying the tac-IS21 construct. The sequences located between the IS21 elements in (IS21)2, 3 bp in R68.45 or 2 bp in pME28, were not recovered in the replicon fusion products. Homologous recombination between the directly oriented IS21 elements in the fusion products led to plasmids with a single IS21 insertion. Analysis of the latter showed that IS21 had a low, but not totally random specificity of insertion and created target duplications of 4 bp (occasionally 5 bp).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1976

The genetic structure of a tribal population, the Yanomama Indians. XIV. Clines and their interpretation.

The Yanomama Indians are a South American tribe distributed over an irregular area approximately 200 X 300 miles. The gene frequencies observed at 12 loci in 47 villages within this area have been analyzed for the occurrence of clines. Apparently significant clines are observed for alleles of the Rh, MNSs, Kidd, Gm, Inv and serum albumin system. Available data concerning recent tribal expansion and admixture permit a tentative analysis of the causes of these clines. Although the action of selection cannot be rigorously excluded, it seems unlikely to be the major couse. Admixture with surrounding tribes plays a role which can be quantified because of the fortuitous cicumstance of two genetic markers for admixture. It is suggested that an important factor in the origin of these clines is the manner in which the tribe has recently expanded through successive village fissionings and a predominantly centrifugal pattern of village migration.

Alleles↗
PubMedDate not supplied

Isonymy and the genetic structure of Switzerland. II. Isolation by distance.

Isolation by distance in Switzerland was detected comparing the surname distributions between Cantons. The decay of isonymy with geographic distance between Cantons was consistent with Malecot's exponential decay of kinship. Lasker's distance was defined as the negative value of the logarithm of isonymy between localities, and it was found that it is linearly and significantly correlated with the log of geographic distance, both within and between languages. The peculiar geographic and linguistic structure of the Confederation, where mountain barriers exist at short distances separating different languages, might explain the rapid changes in surname similarity. It was predicted that the frequency of markers linked to the Y chromosome would show a similar association with distance in Switzerland.

Genetics, Population↗
PubMed2002

Influence of recombination and niche separation on the population genetic structure of the pathogen Streptococcus pyogenes.

The throat and skin of the human host are the principal reservoirs for the bacterial pathogen Streptococcus pyogenes. The emm locus encodes structurally heterogeneous surface fibrils that play numerous roles in virulence, depending on the strain. Isolates harboring the emm pattern A-C marker exhibit a strong tendency to cause throat infection, whereas emm pattern D strains are usually recovered from impetigo lesions; as a group, emm pattern E organisms fail to display obvious tissue tropisms. The peak incidence for streptococcal pharyngitis and impetigo varies with season and locale, leading to wide spatial and temporal distances between throat and skin strains. To assess any impact of niche separation on genetic variation, the extent of recombinational exchange between emm pattern A-C, D, and E subpopulations was evaluated. Analysis of nucleotide sequence data for internal portions of seven housekeeping loci from 212 isolates provides evidence of extensive recombination between strains belonging to different emm pattern subpopulations. Furthermore, no fixed nucleotide differences were found between emm pattern A-C and D strains. Thus, despite some niche separation created by distinct epidemiological trends and innate tissue tropisms there is little evidence for neutral gene divergence between throat and skin strains. Maintenance of a relationship between emm pattern and tissue tropism in the face of underlying recombination suggests that tissue tropism is associated with emm or a closely linked gene.

Alleles↗
PubMed2002

The genetic structure of the rare lagoonal sea anemone, Nematostella vectensis Stephenson (Cnidaria; Anthozoa) in the United Kingdom based on RAPD analysis.

The sea anemone Nematostella vectensis occurs in lagoons in the United States and along the southern and eastern coasts of the United Kingdom. In the United Kingdom it is considered rare and is threatened, principally through the destruction of lagoonal habitat. Random amplified polymorphic DNA (RAPD) data from populations across most of the rane of N. vectensis in the United Kingdom revealed that 61% of individuals had an identical genotype, the frequency of which varied from 0.01 to 1.00. These data provide strong evidence for predominantly clonal reproduction and for the existence of a 'general-purpose genotype' in the UK populations. Alternatively, the low levels of genetic variation observed in some N. vectensis populations may have resulted if they were founded from very few successful individuals from the United States. Analysis of molecular variance (amova) showed significant genetic differentiation between lagoons with no large-scale pattern of geographical variation. This result is consistent with occasional passive or anthropogenic dispersal of low numbers of individuals between lagoons followed by asexual proliferation of immigrants. Transplantation of individuals of the predominant (general-purpose) genotype, for conservation purposes, will probably stand a good chance of survival given its prevalence throughout the United Kingdom.

Analysis of Variance↗
PubMed2004

[Impacts of malathion on population genetic structure of Oxya chinensis].

Allozyme electrophoresis was employed to compare the difference in mortality among the genotypes at two polymorphic loci of Pgm and Me of grasshopper Oxya chinensis individuals acutely exposed to 1.5g/L malathion which resulted in 56% mortality in 24 hours. The selective lethal effects were observed among the genotypes at Pgm locus but not at Me locus. It is noted that the genotype Pgm-ab experienced the highest mortality (80%), whereas Pgm-bb and Pgm-bc were 49%, lower than the average. The chi(2) tests showed significant difference in morality between Pgm-bb and Pgm-cc. After exposure the allele frequency of Pgm-b showed a notable increase among surviving individuals. The cluster analysis based on Roger's genetic distance indicated that the acute exposure to malathion can cause differentiation in genetic composition at population level in Oxya chinensis. Because malathion is commonly used as the insecticide for grasshopper control, the data obtained in this study suggest that the similar genotype-mortality effects may occur in crop fields.

Alleles↗
PubMed1975

The genetic structure of a tribal population, the Yanomama Indians XI. Gene frequencies for 10 blood groups and the ABH-Le secretor traits in the Yanomama and their neighbors; the uniqueness of the tribe.

In this paper we present the results of blood group typings for a total of 33 villages distributed among five South American Indian tribes--Yanomama (21 villages), Makiritare (eight villages), Macushi (two villages), Piaroa (one village), and Wapishana (one village). These new results for the Yanomama and Makiritare tribes have been combined with those previously reported to allow a better appreciation of the distribution of allelic frequencies in the tribes. The relationship of the Yanomama to other South American Indian tribes is investigated using data on six polymorphic loci (Rh, MNS, Fy, Jk, Di, Hp). By use of four genetic measures (two of genetic relationship and two of genetic diversity), we demonstrate that the Yanomama are genetically unique among a sample of 20 South American tribes. In addition, the Yanomama show somewhat less genetic diversity for the six loci analyzed than the average South American tribe. Taken together, these results indicate a rather long period of isolation for the population antecedent to the Yanomama--perhaps since the time of entry of man into the South American continent. The pattern of genetic relationships and genetic diversity for the 20 tribes is consistent with the hypothesis that evolution in South America proceeded by a process of fission-fusion leading to isolation of subpopulations with subsequent genetic differentiation as a consequence of population isolation. The uniqueness of the Yanomama appears to stem entirely from such a process, there being no evidence of any selective differential for the loci analyzed.

ABO Blood-Group System↗