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At least 235 records · Page 13Linked to original sources
PubMed2001

Allozyme diversity and population structure of Japanese and Korean populations of wild radish, Raphanus sativus var. hortensis f. raphanistroides (Brassicaceae).

Raphanus satiuus var. hortensis f. raphanistroides (wild radish: Brassicaceae) is an insect-pollinated wild plant that grows mainly on beaches in East Asia. Starch gel electrophoresis was used to investigate the allozyme diversity and genetic structure of 25 Japanese and 9 Korean populations of this plant. Although the Korean populations were small, isolated, and patchily distributed, they maintained a high level of genetic diversity; the average percentage of polymorphic loci was 63.1%, the mean number of alleles per locus was 2.27, and the average heterozygosity was 0.278. The corresponding estimates for these parameters in the Japanese populations were 53.3%, 2.26, and 0.278. These estimates are considerably higher than those from species with similar life history and ecological characteristics, but they are lower than those from R. raphanistrum, the wild radish that grows in Europe and the U.S.A. The combination of an insect-pollinated, outcrossing breeding system, large population sizes, gene flow from cultivated radish population, and a propensity for high fecundity may explain the high level of genetic diversity within wild populations.

Alleles↗
PubMed2002

Something old, something new: do genetic studies of contemporary populations reliably represent prehistoric populations of Pacific Rattus exulans?

Through our research focusing on genetic studies of both ancient and extant commensal animals in the Pacific for addressing issues of population origins and mobility in the region, we have been able to process a large number of archaeological faunal remains that we can compare to modern samples from the same islands. These comparisons shed light on and provide specific evidence for Rattus exulans population change through time. This information may provide a model for understanding human populations in the region and will illustrate the complexities of using data obtained from modern populations to infer prehistoric relationships. Two case studies are presented here-analyses of modern and archaeological populations of R. exulans from both Chatham Island and New Zealand. These two cases provide very different pictures regarding the relationship between the archaeological and the extant populations.

Animals↗
PubMed2003

Genetics and population history of Caucasus populations.

We describe aspects of genetic diversity in several ethnic populations of the Caucasus Mountains of Daghestan using mitochondrial DNA sequences and a sample of 100 polymorphic Alu insertion loci. The mitochondrial DNA (mtDNA) sequences are like those of Europe. Principal coordinates and nearest neighbor statistics show that there is little detectable structure in the distances among populations computed from mtDNA. The Alu frequencies of the Caucasus populations suggest that they have undergone more genetic drift than most other groups since the dispersal of modern humans. Genetic differences among these populations are not large; instead, they are of the same order as distances among populations of Europe. We compare two methods of inference about the demography of ancient colonizing populations from Africa, one based on conventional FST statistics and one based on mean Alu insertion frequencies. The two approaches agree reasonably well if we assume that there was demographic growth in Africa before the diaspora of ancestors of contemporary regional human groups outside Africa.

DNA, Mitochondrial↗
PubMed2006

European population substructure: clustering of northern and southern populations.

Using a genome-wide single nucleotide polymorphism (SNP) panel, we observed population structure in a diverse group of Europeans and European Americans. Under a variety of conditions and tests, there is a consistent and reproducible distinction between "northern" and "southern" European population groups: most individual participants with southern European ancestry (Italian, Spanish, Portuguese, and Greek) have >85% membership in the "southern" population; and most northern, western, eastern, and central Europeans have >90% in the "northern" population group. Ashkenazi Jewish as well as Sephardic Jewish origin also showed >85% membership in the "southern" population, consistent with a later Mediterranean origin of these ethnic groups. Based on this work, we have developed a core set of informative SNP markers that can control for this partition in European population structure in a variety of clinical and genetic studies.

Arthritis, Rheumatoid↗
PubMed2005

Modeling linkage disequilibrium in natural populations: the example of the Soay sheep population of St. Kilda, Scotland.

The use of linkage disequilibrium to localize the genes underlying quantitative traits has received considerable attention in the livestock genetics community over the past few years. This has resulted in the investigation of linkage disequilibrium structures of several domestic livestock populations to assess their potential use in fine-mapping efforts. However, the linkage disequilibrium structure of free-living populations has been less well investigated. As the direct evaluation of linkage disequilibrium can be both time consuming and expensive the use of simulations that include as many aspects of population history as possible is advocated as an alternative. A simulation of the linkage disequilibrium structure of the Soay sheep population of St. Kilda, Scotland, is provided as an example. The simulated population showed significant decline of linkage disequilibrium with genetic distance and low levels of background linkage disequilibrium, indicating that the Soay sheep population is a viable resource for linkage disequilibrium fine mapping of quantitative trait loci.

Age Factors↗
PubMed1992

Optimal effective population size for the global population of black and white dairy cattle.

The replacement of other black and white cattle strains by the North American Holstein breed, which itself is dominated by a small number of elite sires, has reduced the genetic diversity of the global population. Intense selection on a global basis leads to rapid genetic improvement but reduces effective population size. The optimal global effective population size was chosen to maximize the net present value of all future benefits from the breeding program. Two separate discount rates were used to reflect concerns about the long-term costs of small effective population size. This led to a higher optimal number of bull-sires than in past analyses. The optimum was sensitive to the magnitude of inbreeding depression and to the discount rates, but not to the variance caused by new mutations and the size of the world population. The genetic correlation between the breeding objectives of different AI studs controls the extent to which they all select the same sires of sons and, hence, affects the global effective population size. The prediction is made that different countries will select partially different sires, but genetically isolated strains will not reemerge. A better global breeding program is likely when selection of sires takes account of inbreeding depression and small genotype by environment interactions.

Animals↗
PubMedDate not supplied

[Development of the population size, contribution of foreign breeds, inbreeding and degree of relationships of the entire Hanoverian scenthound population registered in the stud book of the kennel club Hirschmann e.V].

The entire dog population of Hanoveranian Scenthounds registered since the foundation of the kennel club Hirschmann in the year 1894 was analysed for the development of the inbreeding and relationship coefficient and the contribution of Hanoveranian Scenthound population of foreign countries. The analyses were performed using all available pedigree information. In the history, the breeding of the Hanoveranian Scenthound was difficult because of the low number of breeding dogs which was additionally reduced during World War I and II. The mean coefficient of inbreeding of the entire German population was 6.35%. From 1950 to 1990, the mean coefficient of inbreeding increased from 8.3% to 9.7%. In the birth years from 1990 to 2002, the mean coefficient of inbreeding decreased slightly to 9.2%. The rates of inbreeding decreased since 1950. For the last 8 generations the increase of the coefficients of inbreeding per generation was 0.71%. The mean degree of relationship of the entire population was 7.17%, whereby values higher than 75% were found. Gene contributions of 8 other European stud books for the Hanoveranian Scenthound could be found in the German population. Hereby, the Austrian Hanoveranian Scenthounds had the largest impact on the German population with 24.4%. The proportion of genes from the German stud book amounted to 67%.

Animals↗
PubMed2004

[Effect of nitrogen fertilization and square loss on cotton aphid population, cotton leafhopper population and cotton yield].

The study on the effects of nitrogen fertilization (0-450 kg x hm(-2)) and square loss (0-12 x plant(-1)) on cotton aphid population, cotton leafhopper population and cotton yield showed that there were no significant differences in cotton aphid population, cotton leafhopper population, and numbers of effective bolls between transgenic Bt cotton and non-transgenic cotton. Cotton aphid populations on the two cottons were significantly influenced by nitrogen fertilization and by the interaction of nitrogen fertilization and square loss, while leafhopper populations were not significantly influenced by them. Nitrogen fertilization at squaring and flowering stage was one of important factors affecting cotton yield. There was a positive correlation between the application rate of nitrogen fertilizer and cotton yield, but a negative correlation between the number of lost square per plant and the yield of the two cottons.

Animals↗
PubMed2004

[Differentiation of the mitochondrial subhaplogroup U4 in the populations of Eastern Europe, Ural, and Western Siberia: implication to the genetic history of the Uralic populations].

Phylogenetic relationships between the sequences of the mitochondrial DNA (mtDNA) hypervariable segment 1, belonging to subhaplogroup U4, were examined in the populations of Eastern Europe, Ural, and Northwest Siberia. It was shown that the frequency of subhaplogroup U4, as well as its proportion in the U-component of the gene pools, increased eastwards, reaching maximum values in the populations of Northwest Siberia. Phylogenetic analysis it was showed that the appearance of specific U4-lineage (16113C-16356-16362) in the ancestors of Mansi was most likely caused by its divergence from the East European cluster 16356-16362 in the Late Upper Paleolithic (18566 +/- 12915 years before present). Other U4 mtDNA lineages (16189-16356 and 16311-16356), typical mostly of the indigenous populations of Northwest Siberia (Mansi, Nganasans, and Kets) may have formed during the Neolithic-early Bronze Age (6055 +/- 3599 years before present, on average). It seems likely that the isolation of ancient populations inhabiting the region between the Ob' and Yenisei rivers was the key factor, providing the appearance of the unique Caucasoid mtDNA lineages in their gene pools. These results were consistent with the traditional point of view on the mixed origin of the Finno-Ugric populations of the Volga-Ural region and West Siberia, resulted from the genetic relationships between the populations of Europe and Asia.

DNA, Mitochondrial↗
PubMed1990

[Late antiquity constitutional historical and social-anthropologic observations of middle and north European populations at the time of population migrations].

This review on reports of mostly late antique authors concerning the physical appearance of Teutonic and Nordic populations of the so-called "Völkerwanderungszeit" is part of an extensive study of possible nutritional effects on somatotypes in early periods of the German history. It is linked up with a similar study on Teutonics of protohistorical periods (Wurm 1986a). The authors of the late antique periods were again and again impressed by the comparatively tall and sturdy stature as well as by the permanent martial aggressiveness and the considerable population growth of Northern peoples. One can observe a marked social variability in the distribution of somatotypes, and one can suppose, too, that physical superiority was favourable to social rise. However, as compared with Roman soliders the Teutonic-Nordic warriors of the "Völkerwanderungszeit" were obviously inferior as far as permanent physical stress is concerned. This seems to be caused by nutritional differences. Furthermore, the repeatedly claimed inclination of Teutonic-Nordic populations to a considerable consumption of alcoholics seems also be due to nutritional factors. Hair and eye colour of these populations are described by the various antique authors in a different way. The reported geographical differences in the distribution of hair and eye colour seem to indicate considerable Celtic elements in certain populations, which originally were designed as Teutonics. Apart from that no clear anthropological differences were recorded between different populations of this period.

Body Constitution↗
PubMed1988

[Population genetics study of functional brain asymmetry in the native and immigrant populations of northeastern USSR. I. Sex-age distribution and familial data].

Clearly definable polymorphism of hemisphere interrelations represented by three phenotypes was established by the method of EEG cross-correlation analysis. Each phenotype of the three, representing polymorphism, is characterized by marked specificity of perception and the processing of information, which determines certain integral physiological characteristics of individuals. Phenotype frequencies in aboriginal and new-come populations of the North-East of the USSR differ significantly. In comparison with the inhabitants, Moscow Russians of Magadan are significantly closer to aboriginal population, judging by their frequency distribution, and this may be due to the strategy specificity in adaptation of populations to environmental conditions. Significant difference in phenotype frequencies is shown in representatives of both sexes, this being more pronounced in the aboriginal population. The establishment of interhemispheric reaction type by approx. 10th year of individual's life is confirmed. Phenotype frequency correlations, depending on parental phenotype, were analyzed in children. The role of genetic and environmental factors in manifestation of the hemisphere relationship type is discussed. Rationality of the population analysis of hemisphere asymmetry types is grounded, according to the study of behavioural genetics and population adaptation.

Age Factors↗
PubMed1977

Experimental population genetics of meiotic drive systems. I. Pseudo-Y chromosomal drive as a means of eliminating cage populations of Drosophila melanogaster.

The experimental population genetics of Y-chromosome drive in Drosophila melanogaster is approximated by studying the behavior of T(Y;2),SD lines. These exhibit "pseudo-Y" drive through the effective coupling of the Y chromosome to the second chromosome meiotic drive locus, Segregation distorter (SD). T(Y;2),SD males consequently produce only male offspring. When such lines are allowed to compete against structurally normal SD(+) flies in population cages, T(Y;2),SD males increase in frequency according to the dynamics of a simple haploid selection model until the cage population is eliminated as a result of a deficiency in the number of adult females. Cage population extinction generally occurs within about seven generations.-Several conclusions can be drawn from these competition cage studies:(1) Fitness estimates for the T(Y;2),SD lines (relative to SD(+ )) are generally in the range of 2-4, and these values are corroborated by independent estimates derived from studies of migration-selection equilibrium. (2) Fitness estimates are unaffected by cage replication, sample time, or the starting frequency of T(Y;2),SD males, indicating that data from diverse cages can be legitimately pooled to give an overall fitness estimate. (3) Partitioning of the T(Y;2),SD fitnesses into components of viability, fertility, and frequency of alternate segregation (Y + SD from X + SD(+)) suggests that most of the T(Y;2),SD advantage derives from the latter two components. Improvements in the system might involve increasing both the viability and the alternate segregation to increase the total fitness. While pseudo-Y drive operates quite effectively against laboratory stocks, it is less successful in eliminating wild-type populations which are already segregating for suppressors of SD action. This observation suggests that further studies into the origin and rate of accumulation of suppressors of meiotic drive are needed before an overall assessment can be made of the potential of Y-chromosome drive as a tool for population control.

Animals↗
PubMed1980

[Planktonic and bacterial population dynamics during experimental production of natural marine phytoplankton. II. Structure and physiology of populations and their interactions].

During the spring, an experiment was conducted on the production of natural phytoplankton in a continuous flow layout of large capacity, and an analysis was made of the simultaneous evolution of microplanktonic populations (taxonomic composition, diversity, class ranges, and energetic charge) and of bacterial populations (structure, diversity, dominances, and cetabolic potentialities). Oligotrophic initial conditions were charcterized by a poor (0.22 umg of chlorphyll a/L) and diversified (pigment diversity = 4.5) phytoplankton with nanoplanktonic dominance associated with several benthic type diatoms. Bacterial flora, in which pseudomonads were dominant (54.5%), were also diversified (Shannon index H = 3.57). Metabolic potentialities of these bacterial communities were several. Enrichment of the milieu caused the selection and development of a small number of algal species dominated by the diatoms skeletonema costatum (64 x 106/L) and Chaetoceros (3.2 x 106/L) leading to a paucispecific population with a large biomass, a pigment diversity of 1.97, and a chlorophyll a concentration of 25.08 mu/L. The bacterial community then because diversified (H = 4.12) and, although pseudomonads remained dominant (62%), a larger use of organic micromolecules was noted. The establishment of this phytoplanktonic community was followed by a zooplanktonic development in which larger species succeeded smaller ones (ciliates, tintinnides, rotifers, and copepods) corresponding to the global increase of the phytobiomass. Although this system appeared to be in a phase of relative stability, a decease in the energetic charge showed a disturbance in the physiological state of the planktonic populations. These phenomena led to the vanishing of the diatom's dominance (Chaetoceros, and then S. costatum) and its replacement by nanoplankton (123 x 106 cells/L) and dinoflagellates (300000 cells/L). A modification in the organic wealth of the milieu with the addition of particular complex material that was not or little degraded caused deep disturbances in the bacterial populations. Their diversity reached a very low level (H = 1.56 to 2.25) with a proliferation of vibrions (up to 74%) well equipped with exoenzymes, but more restricted in their nutritional versatility (marked preference for organic macromolecules). During the final phase of experimentation, despite a change in qualitative composition and a more important biomass, microplanktonic and bacterial populations returned to a diversified state nearing that of the initial conditions (pigment diversity = 3.2; H = 3.37).

Adenosine Triphosphate↗
PubMed1995

Population review. Structure and distribution of the population.

This article is the first in a series of articles reviewing the changing composition of the population of the United Kingdom. The series is a follow-up to the demographic reviews published in the mid-1970s and mid-1980s (see In Brief, page 2). This first article gives a summary view of the changes since the early Seventies in the structure and distribution of the UK population, and also takes account of population projections for future years. It begins by describing changes in the total population. The review then goes on to consider changes in sex ratios, age distribution, marital status, the regional distribution of the UK resident population, population density, ethnicity and household composition.

Adolescent↗
PubMed1996

[Change in sex ratio of a Drosophila population in relation to population size].

Changes in sex ratio with population size fluctuations were studied in natural and cage populations of Drosophila. It was shown that the proportion of females decreased with an increase in population size both in natural and laboratory populations. If laboratory populations were maintained on a poor diet, this effect was absent. The amplitude of number fluctuation was shown to be higher in males than in females. The possible role of density-dependent selection on sex in the control of population size dynamics is discussed.

Animals↗
PubMed1998

Siberian population of the New Stone Age: mtDNA haplotype diversity in the ancient population from the Ust'-Ida I burial ground, dated 4020-3210 BC by 14C.

On the basis of analysis of mtDNA from skeletal remains, dated by 14C 4020-3210 BC, from the Ust'-Ida I Neolithic burial ground in Cis-Baikal area of Siberia, we obtained genetic characteristics of the ancient Mongoloid population. Using the 7 restriction enzymes for the analysis of site's polymorphism in 16,106-16,545 region of mtDNA, we studied the structure of the most frequent DNA haplotypes, and estimated the intrapopulational nucleotide diversity of the Neolithic population. Comparison of the Neolithic and modern indigeneous populations from Siberia, Mongolia and Ural showed, that the ancient Siberian population is one of the ancestors of the modern population of Siberia. From genetic distance, in the assumption of constant nucleotide substitution rate, we estimated the divergence time between the Neolithic and the modern Siberian population. This divergence time (5572 years ago) is conformed to the age of skeletal remains (5542-5652 years). With use of the 14C dates of the skeletal remains, nucleotide substitution rate in mtDNA was estimated as 1% sequence divergence for 8938-9115 years.

Asian People↗
PubMed1999

Population genetic data on loci LDLR, GYPA, HBGG, D7S8 and GC in the Bangkok population compared with rural Thais from Trat province.

Prior to the introduction of any DNA marker as a tool for person identification and paternity test in certain ethnic groups, a population genetic database should be constructed. Using multiplex primers in single tube polymerase chain amplification, 5 loci of unrelated genes in the PM Amplitype kit (Perkin Elmer) were studied in two Thai population groups: 228 DNA samples were extracted from blood collected at the Borai rural area in Trat province; another 123 DNA samples were collected at the outpatient clinic, Department of Forensic Medicine, King Chulalongkorn Memorial Hospital, Bangkok. Analysis of alleles and genotypes was performed after reversed dot blot hybridization of PCR products to allelic sequence specific probes immobilized on the membrane strip followed by nonradioisotopic detection according to the manufacturer's protocol. Population genetic statistic parameters including discrimination power (DP), the probability of matching (PM), power of exclusion for trio (PE trio) and typical paternity index (PI typical) were computed. Both Thai population groups showed no significant deviation from the Hardy Weinberg Expectation (HWE). The combined DP of all 5 loci in the PM Amplitype markers was 0.993636 for rural Thais and 0.994409 for Thais from Bangkok. The combined PM for rural Thais and those living in Bangkok was 0.006364 and 0.005591, respectively. The combined PE trio was 0.696825 and 0.698875 in both Thai population groups and the combined PI typical values were < 1.0. In conclusion, person identification using PM Amplitype DNA markers was efficient and satisfactory within certain limits. Hence, the application of PM Amplitype DNA markers for paternity tests should be cautiously considered and applied in combination with other parameters.

Alleles↗