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PubMed1984

Population genetics of transposable elements.

Transposable elements are DNA sequences that can move or duplicatively transpose on the chromosome. A simple model of transposable elements was studied, and the frequency spectrum, allelism, and identity coefficients at equilibrium were obtained. In the analyses, the two cases of asexual haploid with no recombination and diploid with free recombination were treated separately. It was shown that the multiple allele theory of population genetics is applicable to the problems of frequency spectrum and allelism. On the other hand, identity coefficients may be formulated analogously to the treatment of concerted evolution of multigene families. Results indicate that, except for allelic identity, the model of transposable elements and that of multigene families predict similar values of identity coefficients.

Biometry↗
PubMed1997

Presence of bacteriophage Aa phi 23 correlates with the population genetic structure of Actinobacillus actinomycetemcomitans.

Several bacteriophages associated with the oral bacterium Actinobacillus actinomycetemcomitans have been identified. Lysogeny might affect the virulence of this bacterium, which has been implicated in the etiology of juvenile and adult periodontitis. We have determined the presence of bacteriophage Aa phi 23-related DNA sequences among 185 A. actinomycetemcomitans strains belonging to 2 well-characterized collections and have related the findings to the population genetic structure of the collections. 2 cloned Aa phi 23-specific DNA probes were used in Southern blot hybridization experiments to detect homologous sequences in whole-cell DNA of the strains. DNA from 65 (35%) of the 185 strains hybridized to either of the DNA probes. The majority (74%) of the hybridizing strains showed an identical hybridization pattern, indicating presence of phage Aa phi 23. Whole-cell DNA from the remaining hybridizing strains hybridized to the probes with different patterns, indicating that DNA sequences related to but different from phage Aa phi 23 occur in these strains. The majority (81%) of the strains which harbored phage Aa phi 23 were of serotype a, whereas serotype d strains appeared to be resistant to infection with this phage. There was a clear correlation between hybridization patterns and genetic subdivisions based on our previous population genetic analyses of A. actinomycetemcomitans. However, there was no significant correlation between occurrence of Aa phi 23 among A. actinomycetemcomitans strains and the periodontal status of the patients from whom the isolates were obtained, suggesting that this bacteriophage does not significantly influence the virulence of A. actinomycetemcomitans.

Abscess↗
PubMed1997

Short tandem repeat HumACTBP2 (SE33) and HumVWA: population genetic study on a north Italian population.

Allele frequencies at the short tandem repeat (STR) loci HumACTBP2 and HumVWA were determined in 118 unrelated individuals from Northern Italy (Milan area). For locus HumACTBP2 (SE33) a total of 39 alleles was observed. Furthermore, two interalleles (N18m+N19m) and one allele (> N35) were found which were not observed in a wider German population survey (n = 560). For the STR system HumVWA, 7 alleles could be detected. Both systems showed no significant deviation from Hardy-Weinberg equilibrium. A comparison of Italian and German population data revealed no significant differences for locus HumVWA, while significant differences were observed for locus HumACTBP2.

Actins↗
PubMed2000

The molecular population genetics of regulatory genes.

Regulatory loci, which may encode both trans acting proteins as well as cis acting promoter regions, are crucial components of an organism's genetic architecture. Although evolution of these regulatory loci is believed to underlie the evolution of numerous adaptive traits, there is little information on natural variation of these genes. Recent molecular population genetic studies, however, have provided insights into the extent of natural variation at regulatory genes, the evolutionary forces that shape them and the phenotypic effects of molecular regulatory variants. These recent analyses suggest that it may be possible to study the molecular evolutionary ecology of regulatory diversification by examining both the extent and patterning of regulatory gene diversity, the phenotypic effects of molecular variation at these loci and their ecological consequences.

Adaptation, Physiological↗
PubMed2001

Hybridization and population genetics of two macaque species in Sulawesi, Indonesia.

This study investigates hybridization and population genetics of two species of macaque monkey in Sulawesi, Indonesia, using molecular markers from mitochondrial, autosomal, and Y-chromosome DNA. Hybridization is the interbreeding of individuals from different parental taxa that are distinguishable by one or more heritable characteristics. Because hybridization can affect population structure of the parental taxa, it is an important consideration for conservation management. On the Indonesian island of Sulawesi an explosive diversification of macaques has occurred; seven of 19 species in the genus Macaca live on this island. The contact zone of the subjects of this study, M. maura and M. tonkeana, is located at the base of the southwestern peninsula of Sulawesi. Land conversion in Sulawesi is occurring at an alarming pace; currently two species of Sulawesi macaque, one of which is M. maura, are classified as endangered species. Results of this study indicate that hybridization among M. maura and M. tonkeana has led to different distributions of molecular variation in mitochondrial DNA and nuclear DNA in the contact zone; mitochondrial DNA shows a sharp transition from M. maura to M. tonkeana haplotypes, but nuclear DNA from the parental taxa is homogenized in a narrow hybrid zone. Similarly, within M. maura divergent mitochondrial DNA haplotypes are geographically structured but population subdivision in the nuclear genome is low or absent. In M. tonkeana, mitochondrial DNA haplotypes are geographically structured and a high level of nuclear DNA population subdivision is present in this species. These results are largely consistent with a macaque behavioral paradigm of female philopatry and obligate male dispersal, suggest that introgression between M. maura and M. tonkeana is restricted to the hybrid zone, and delineate one conservation management unit in M. maura and at least two in M. tonkeana.

Animals↗
PubMed2006

Population genetic structure of the malaria vector Anopheles moucheti in south Cameroon forest region.

We used recently developed microsatellite DNA markers to explore the population genetic structure of the malaria vector, Anopheles moucheti. Polymorphism at 10 loci was examined to assess level of genetic differentiation between four A. moucheti populations from South Cameroon situated 65-400 km apart. All microsatellite loci were highly polymorphic with a number of distinct alleles per locus ranging from 9 to 17. Fst estimates ranging from 0.0094 to 0.0275 (P < 0.001) were recorded. These results suggest a very low level of genetic differentiation between A. moucheti populations. The recently available microsatellite loci revealed useful markers to assess genetic differentiation between geographical populations of A. moucheti in Cameroon.

Alleles↗
PubMed1981

[Population genetics study of rheumatism in the Dolgans of the Taimyr].

The results of medical-genetic examination of population in five villages of Taimir have been presented. Among them 824 dolgans (aborigines) have been inspected. The prevalence of rheumatism is in average 3,23%. The frequency of rheumatism in the southern subpopulation was higher, than in the North. Analysis of pedigrees has shown family aggregation of rheumatism which correlated with theoretically expected according to recessive hypothesis. Investigations of genetic markers have shown important distinction of rheumatic patients from population on ABC and Hp.

Adolescent↗
PubMed2002

Mating system and population genetic structure of an androdioecious tree, Fraxinus lanuginosa Koidz. (Oleaceae) in northern Japan.

Models for the maintenance of androdioecy have suggested that selfing of hermaphrodites decreases the frequency of males in a population (the "male frequency"). To test this hypothesis, we used electrophoretic allozyme methods to study the mating system and population genetics of an androdioecious tree, Fraxinus lanuginosa, which exhibits large variations in male frequency among subpopulations in central Hokkaido (northern Japan). We estimated the outcrossing rates by using seeds assayed at three polymorphic loci, and found that the multilocus outcrossing rate (t(m)) increased with increasing male frequency (q) (t(m) = 0.69 to 0.99, q = 0.11 to 0.59). Fixation indices (F(j)) estimated from these t(m) values ranged from 0.006 to 0.185, and were significantly greater than zero in plots with a low male frequency (q or = 0.47). However, fixation indices at the late life stage (F(a)) were not significantly different from zero at five loci (F(a) = 0.056 to 0.101, q = 0.11 to 0.61), and the F(a) values were lower than the F(j) values in several of the plots where both values were measured. These results indicate that inbreeding depression substantially decreases the proportion of selfed progeny in partially self-fertilising subpopulations. A theoretical model for the maintenance of androdioecy showed expected male frequencies significantly lower than the observed values in plots with high male frequency (q = 0.59 to 0.61), although the differences between the expected and observed values of male frequencies were not significant in plots with intermediate or low male-frequencies (q = 0.11 to 0.47). In this paper, the factors are discussed that affect variations in the male frequency among subpopulations of F. lanuginosa based on these findings.

Animals↗
PubMed2005

The nk model and population genetics.

The nk model of fitness interactions is examined. This model has been used by previous authors to investigate the effects of fitness epistasis on substitution dynamics in molecular evolution, and to make broader claims about the importance of epistasis. To examine these claims, an infinite-allele approximation is introduced. In this limit, it is shown that the nk model is, at an appropriate level of description, formally identical to the non-epistatic House-of-Cards model--a well-studied model in theoretical population genetics. It is further shown that in many parameter regimes, the analytical results obtained from this infinite-allele approximation are very close to results from the full nk model (with a finite number of alleles per locus). The findings presented shed light on a number of previous results.

Alleles↗
PubMed1992

HLA-DR polymorphism in a Senegalese Mandenka population: DNA oligotyping and population genetics of DRB1 specificities.

HLA class II loci are useful markers in human population genetics, because they are extremely variable and because new molecular techniques allow large-scale analysis of DNA allele frequencies. Direct DNA typing by hybridization with sequence-specific oligonucleotide probes (HLA oligotyping) after enzymatic in vitro PCR amplification detects HLA allelic polymorphisms for all class II loci. A detailed HLA-DR oligotyping analysis of 191 individuals from a geographically, culturally, and genetically well-defined western African population, the Mandenkalu, reveals a high degree of polymorphism, with at least 24 alleles and a heterozygosity level of .884 for the DRB1 locus. The allele DRB1*1304, defined by DNA sequencing of the DRB1 first-domain exon, is the most frequent allele (27.1%). It accounts for an unusually high DR13 frequency, which is nevertheless within the neutral frequency range. The next most frequent specificities are DR11, DR3, and DR8. Among DRB3-encoded alleles, DR52b (DRB3*02) represents as much as 80.7% of all DR52 haplotypes. A survey of HLA-DR specificities in populations from different continents shows a significant positive correlation between genetic and geographic differentiation patterns. A homozygosity test for selective neutrality of DR specificities is not significant for the Mandenka population but is rejected for 20 of 24 populations. Observed high heterozygosity levels in tested populations are compatible with an overdominant model with a small selective advantage for heterozygotes.

Base Sequence↗
PubMedDate not supplied

[The population genetic aspects of the intestinal microbiological phenotype in healthy humans].

The principle of the formation of the microbiological phenotype in the intestine of healthy persons was studied by the method of the population-genetic analysis. The microbial composition of the intestinal flora of healthy members of 10 complete families (altogether 50 persons) was studied. The study revealed that practically in all cases the variability of the qualitative and quantitative characteristics of the phenotype under study on the levels of both genera and individual microbial species is formed mainly under the influence of environmental factors. The presence of indigenous bacteria in the intestinal microbiocenosis (including Escherichia coli with normal enzymatic properties) is strongly genetically determined.

Adolescent↗
PubMedDate not supplied

Population genetics of Mexican Drosophila. I. Chromosomal variation in natural populations of Drosophila pseudoobscura from Central Mexico.

Drosophila pseudoobscura populations of Central Mexico are chromosomally highly polymorphic. Five gene arangements in the third chromosome are endemic, including the two newly described in the present article. The phylogenetic tree of the gene arrangements known in the species is shown in Figure 1. The ones found in Central Mexico all belong to the Santa Cruz "phylad", while in the northern part of the species area both Santa Cruz and Standard phylads are widespread. Some inferences concerning the evolutionary history of the species are presented.

Animals↗
PubMed1987

[Complex medico-genetic study of the Western Siberian population. II. Population-genetic study of fluorescent chromosome polymorphism in Northern Khanty].

Polymorphisms of fluorescent variants of 469 human karyotypes from five subpopulations of the Northern Khanty were studied. Significant frequency variability of Q-polymorphic variants of chromosomes was shown. Wahlund's variance for 12 chromosome polymorphic segments was 0.0121, while the total inbreeding coefficient was 0.0069 with a negative nonrandom component. Heterozygosity estimated for chromosome fluorescent polymorphism (0.189) agrees well with that for blood group systems and less for enzymes. The frequencies of Q-polymorphic variants corresponded to Hardy-Weinberg equilibrium, except for chromosome 13 which gave the significant excess of heterozygotes. Possible explanations of this phenomenon are discussed.

Adolescent↗
PubMed2006

Population genetics models of competition between transposable element subfamilies.

Transposable elements are one of the major components of genomes. Some copies are fully efficient; i.e., they are able to produce the proteins needed for their own transposition, and they can move and duplicate into the genome. Other copies are mutated. They may have lost their moving ability, their coding capacity, or both, thus becoming pseudogenes slowly eliminated from the genome through deletions and natural selection. Little is known about the dynamics of such mutant elements, particularly concerning their interactions with autonomous copies. To get a better understanding of the transposable elements' evolution after their initial invasion, we have designed a population genetics model of transposable elements dynamics including mutants or nonfunctional sequences. We have particularly focused on the case where these sequences are nonautonomous elements, known to be able to use the transposition machinery produced by the autonomous ones. The results show that such copies generally prevent the system from achieving a stable transposition-selection equilibrium and that nonautonomous elements can invade the system at the expense of autonomous ones. The resulting dynamics are mainly cyclic, which highlights the similarities existing between genomic selfish DNA sequences and host-parasite systems.

DNA Transposable Elements↗
PubMed1991

Population genetic data determined for five different single locus minisatellite probes.

We report on the population genetic data (frequencies of restriction fragments, heterozygosity rates, and mutation rates) obtained by analysis of approximately 1100 Hinfl-digested DNAs from West Germans. Probe G3 detects a common 1.7 kb DNA fragment showing a population frequency of about 13%. All the other fragments detected with probes MS1, MS31, MS43, G3 and YNH24 show frequencies of less than 8%. These data suggest that single locus DNA probes can provide valuable information for parentage evaluation and individualization.

DNA Probes↗
PubMed2004

[ABO blood groups and haemolytic disease of newborns--population-genetic analysis].

Classical works dealing with the possibility of mother-child incompatibility with regard to basic ABO blood groups give contradictory conclusions (e.g.--Matsunaga et al. 1962, Thompson et al. 1991). Bioreproductive and population-genetic indicators have been studied in a sample of live births and in two pregnancy samples characterised by different "a priori" and "a posteriori" risk assessment. The analysis points out that ABO blood groups can influence fertility of different parental pairs, with a possible impact on the assessment of the individual pregnancy risc.

ABO Blood-Group System↗
PubMed1985

Dual processes and an invariance result for exchangeable models in population genetics.

By means of a representation as interactive particle systems, dual processes are constructed for a large class of exchangeable models in population genetics. It is shown that as the population size becomes large these dual processes tend in distribution to a particularly tractable limiting dual process. Properties of the models are analyzed using the duality relationship and approximate expressions are obtained for various quantities. Diffusion approximations follow easily from the invariance result.

Animals↗