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At least 649 records · Page 36Linked to original sources
PubMed1998

Testing a genetic structure of blood-injury-injection fears.

Multivariate genetic analyses were used to examine the genetic and environmental contributions to individual differences in fears of blood, injury, and injections in 659 twin pairs who completed questions concerning fear and fainting around blood, injury, and injections, and fainting in situations not involving blood, as well as the personality scales of Neuroticism, and Harm Avoidance. There was significant familial aggregation of blood fears but univariate analyses were unable to distinguish between additive genetic or shared environmental variables, or both, as the cause. The same was true of blood fainting. Non-blood-injury fainting was best explained by a model assuming shared and unique environmental variables. However, multivariate genetic analyses, which capitalise on extra information contained by all the covariance terms, indicated that the variance in blood-injury-injection fear was principally attributable to unique environmental events specific to this fear and additive genetic factors shared with fainting. The data are discussed in the context of models of blood-injury phobia that identify the need to consider separate etiological mechanisms for fear and fainting.

Female↗
PubMed2000

Genetic relationships and spatial genetic structure among clonal stocks of Trypanosoma cruzi in Colombia.

Genetic variability in the protozoan causative agent of Chagas' disease, Trypanosoma cruzi, has been analysed in some Latin American countries; Brazil, Bolivia, Chile and Paraguay. Although Colombia is a country displaying enormous biological diversity, few studies have been conducted from the perspective of the population genetics of Trypanosoma cruzi. This study was carried out using 23 Colombian stocks of this protozoan, analysed for 13 isoenzyme loci. The main population genetic results were: (1) Colombia is one of the distribution areas where T. cruzi appears to have the highest genetic variability and heterogeneity in Latin America; (2) the Pgm locus was found in fixed heterozygosis, supporting the presence of diploidy in this organism; (3) the absence of segregating genotypes and the absence of Hardy-Weinberg equilibrium support the view of the existence of a clonal structure as claimed by Tibayrenc and Ayala. Nevertheless, one characteristic of clonal structure, that of over-representation of some identical zymodemes in vast areas of varying environmental conditions, was not found in Colombia. In this country, a strong spatial autocorrelation, with a classic structure of regional patches, was observed.

Animals↗
PubMed2002

A simulated annealing approach to define the genetic structure of populations.

We present a new approach for defining groups of populations that are geographically homogeneous and maximally differentiated from each other. As a by-product, it also leads to the identification of genetic barriers between these groups. The method is based on a simulated annealing procedure that aims to maximize the proportion of total genetic variance due to differences between groups of populations (spatial analysis of molecular variance; samova). Monte Carlo simulations were used to study the performance of our approach and, for comparison, the behaviour of the Monmonier algorithm, a procedure commonly used to identify zones of sharp genetic changes in a geographical area. Simulations showed that the samova algorithm indeed finds maximally differentiated groups, which do not always correspond to the simulated group structure in the presence of isolation by distance, especially when data from a single locus are available. In this case, the Monmonier algorithm seems slightly better at finding predefined genetic barriers, but can often lead to the definition of groups of populations not differentiated genetically. The samova algorithm was then applied to a set of European roe deer populations examined for their mitochondrial DNA (mtDNA) HVRI diversity. The inferred genetic structure seemed to confirm the hypothesis that some Italian populations were recently reintroduced from a Balkanic stock, as well as the differentiation of groups of populations possibly due to the postglacial recolonization of Europe or the action of a specific barrier to gene flow.

Algorithms↗
PubMed1975

Molecular and genetic structure of multiple hemoglobins in the eelpout, Zoarces vivparus L.

Six major hemoglobin components are present in the teleostean fish Zoarces viviparus L. Biochemical characterization has led to a molecular model for the polypeptide chain composition of the individual hemoglobins. Only three different chains are involved. They are determined by three different structural loci, as indicated by the genetic variation of the electrophoretic hemoglobin pattern observed in natural populations. Hemoglobins occur that, despite identical chain compositions, have different electrophoretic mobilities. This may be due to a mechanism, known from man, where part of the hemoglobin is blocked by a hexose.

Animals↗
PubMed2005

Genetic structure of the whitefly Bemisia tabaci in the Asia-Pacific region revealed using microsatellite markers.

Bemisia tabaci (Hemiptera: Aleyrodidae) is a haplo-diploid species of sap-feeding insect belonging to the group of insects commonly known as whiteflies. From earlier analyses of mitochondrial and ribosomal markers it has been concluded that in the Asia-Pacific region there were three major indigenous races as well as a large collection of genotypes with no clear association with any race. This new study uses 15 microsatellite loci and demonstrates that the indigenous Asia-Pacific genotypes can be split into six genetic populations with little or no gene flow between them. These bare only superficial similarity to the mitochondrial and ribosomal defined races. Moreover, four of the six can be further split into two subpopulations that again show little evidence gene flow between them. While the patterns reflect a strong geographical structure, physical barriers alone cannot explain all the observed structure. Differential host-plant utilization explained some of the substructure, but could not explain the overall structure. The roles of mating interference and Wolbachia in developing the genetic structure are considered. The lack of gene flow between genetic populations and some subpopulations further suggests that the barriers were either sufficiently impermeable to immigration or that reproductive isolation and competitive interactions were sufficiently strong to prevent gene flow. If the latter is the case, it suggests that there may be as many as 10 morphologically indistinguishable species indigenous to the Asia-Pacific region.

Animals↗
PubMed2001

Brain structure, genetic liability, and psychotic symptoms in subjects at high risk of developing schizophrenia.

BACKGROUND: Structural magnetic resonance imaging (MRI) of the brain in patients with schizophrenia has consistently demonstrated several abnormalities. These are thought to be neurodevelopmental in origin, as they have also been described in first episode cases, although there may be a progressive component. It is not known at which point in development these abnormalities are evident, nor to what extent they are genetically or environmentally mediated. METHODS: One hundred forty-seven high-risk subjects (with at least two affected first or second degree relatives), 34 patients in their first episode, and 36 healthy control subjects received an MRI scan covering the whole brain. After inhomogeneity correction, regions of interest were traced by three group-blind raters with good inter-rater reliability. Regional brain volumes were related to measures of genetic liability to schizophrenia and to psychotic symptoms elicited at structured psychiatric interviews. RESULTS: High-risk subjects had statistically significantly reduced mean volumes of the left and right amygdalo-hippocampus and thalamus, as compared to healthy control subjects. They also had bilaterally larger amygdalo-hippocampi and bilaterally smaller lenticular nuclei than the schizophrenics. High-risk subjects with symptoms had smaller brains than those without. The volumes of the prefrontal lobes and the thalamus were the only consistent associates of genetic liability. CONCLUSIONS: Subjects at high risk of developing schizophrenia have abnormalities of brain structure similar to but not identical to those found in schizophrenia. Our results suggest that some structural abnormalities are genetic trait or vulnerability markers, others are environmentally mediated, and that the development of symptoms is associated with a third overlapping group of structural changes. Particular risk factors for schizophrenia may interact at discrete time points of neurodevelopment with different effects on specific brain regions and may represent relatively distinct disease processes.

Amygdala↗
PubMed2002

Temporal change in the genetic structure between and within cohorts of a marine fish, Diplodus sargus, induced by a large variance in individual reproductive success.

Temporal changes at 16 allozyme loci in the Diplodus sargus population of Banyuls-sur-Mer (Mediterranean Sea, France) were monitored. Temporal genetic variation within a single population was examined over two temporal scales: (i) among three year-classes sampled at the same age, and (ii) within a single year-class sampled three times over a two-year period. We observed a significant change in the genotypic structure within the same cohort during the first two years following settlement and before recruitment into the adult population. In addition, comparison of year-classes showed that cohorts differed significantly one year after settlement, whereas they became similar later on before recruitment into the adult population. The observed changes in the genetic structure within and between year-classes may be the result of complex selective processes or genetic drift. Linkage disequilibrium and genetic relatedness data suggest that these changes are due to large variation in reproductive success, followed by homogenization through adult movement. Overall, these results demonstrated a rapid genetic change within a population.

Animals↗
PubMed1999

Genetic structure of island populations of the anurans rana temporaria and bufo bufo

Amphibians have traditionally been considered to have low dispersal ability and they have become a model for studies on the effects of man-made habitat fragmentation on genetic variation and population differentiation. This study examined the genetic population structure in the common frog (Rana temporaria) and the common toad (Bufo bufo) in an archipelago of the northern Baltic Sea. Heterozygosity was not correlated with distance of the island from the mainland nor, in R. temporaria, with effective population size based on census estimates. Generally, no inbreeding was detected in island populations. The overall differentiation among islands was weak, but the FST values were significantly larger in R. temporaria (FST = 0.068) than in B. bufo (FST = 0.019). Most of the differentiation was a result of differences among groups of islands, differentiation within them playing a minor role. Thus, assuming Wright's island model of migration, gene flow was rather high among closely located islands, but longer distances seemed to form a slight dispersal barrier for R. temporaria. Strong gene flow within the study area was confirmed by lack of isolation by distance. The estimated effective population sizes in R. temporaria were small, the average being 32 breeding females per island. The results indicate that gene flow between island populations across the matrix of open, brackish-water sea is extensive and suggest that the anurans are well able to disperse in this natural metapopulation system.

Journal Article↗
PubMed2006

[The population genetic structure analysis via microsatellite loci in new Silkies laying breeds].

Twenty microsatellite markers selected from the chicken GENBANK were analyzed for polymorphism in two new Silkies laying breeds. Allele frequencies were tested by the auto scan on ABI 3100-Avant Genetic Analyzer. The results suggested that the optimization test of multiplex PCR was successful and 18 pairs of microsatellite DNA markers were polymorphic. The average number of alleles detected by a pair of primers was 7.444. The average value of PIC was 0.669. The average observation population heterzygosity of the 18 markers was 0.3962, and the average expected population heterzygosity of the 18 markers was 0.7301. The number of bands tested on the auto scan was higher than that based on band presence or absence on gel, thus it was more suitable for genetic population analysis.

Animals↗
PubMed1995

[Genetic polymorphism and gene geography of the indigenous population of the Ural region. I. Genetic structure of the peoples of the Ural region].

The genetic patterns of 25 populations from seven ethnic groups living in the Ural region (Komi, Komi-Permyaks, Udmurts, Mansi, Nentsy, Tatars, and Chuvashes) were studied. Immunological, biochemical, and physiological markers of the loci ABO, FUT, RH, P, FY, DI, KEL, LU, LE, JK, HP, GC, C'3, TF, PI, ACP1, GLO1, ESD, PGD, PGM1, PTC, and CB were studied. The average ethnic frequencies of the alleles and haplotypes studied were estimated. It was demonstrated that the Ural populations living to the west of the Urals, although of different origin, were more similar genetically than populations of common (Ural) origin living on different sides of the Urals, with respect to the majority of the traits studied.

Alleles↗
PubMed2002

The genetic structure of Cloninger's seven-factor model of temperament and character in a Japanese sample.

Theoretical assumptions regarding the genetic and environmental structure of personality proposed in Cloninger's seven-factor model of temperament and character were verified in a Japanese sample by using the twin method. The Temperament and Character Inventory (TCI) was administered to 296 twin pairs ranging in age from 14 to 28 years old. Among four temperament dimensions (novelty seeking [NS], harm avoidance [HA], reward dependence [RD], and persistence [PS]), HA and PS showed significant additive genetic contributions and no shared environmental effect, supporting the original theoretical assumption. NS and RD could be explained by either genetic or shared environmental factors with nonshared environment. All three character dimensions (cooperativeness [CO], self-directedness [SD], and self-transcendence [ST]) could be explained exclusively by additive contributions and no shared environmental effect. Multivariate genetic analysis indicated that there were no significant associations between NS, HA, and RD, as the theory predicts, and the genetic components of PS, SD, and CO were derived from those of the temperament dimensions. The fourth genetic component, which had a substantial load specifically on ST and overlapped with PS, was identified. Although most of the nonshared environmental effects were trait-specific, the phenotypic correlation between NS and HA could be explained by nonshared environmental overlap.

Adolescent↗
PubMed2004

Genetic structure of the forest herb Primula elatior in a changing landscape.

To investigate whether changes in land use and associated forest patch turnover affected genetic diversity and structure of the forest herb Primula elatior, historical data on landscape changes were combined with a population genetic analysis using dominant amplified fragment length polymorphism markers. Based on nine topographic maps, landscape history was reconstructed and forest patches were assigned to two age classes: young (less than 35 years) and old (more than 35 years). The level of differentiation among Primula populations in recently established patches was compared with the level of differentiation among populations in older patches. Genetic diversity was independent of population size (P > 0.05). Most genetic variation was present within populations. Within-population diversity levels tended to be higher for populations located in older forests compared with those for populations located in young forests (Hj = 0.297 and 0.285, respectively). Total gene diversity was also higher for old than for young populations (Ht = 0.2987 and 0.2828, respectively). The global fixation index FST averaged over loci was low, but significant. Populations in older patches were significantly more differentiated from each other than were populations in recently established patches and they showed significant isolation by distance. In contrast, no significant correlations between pairwise geographical distance and FST were found for populations in recently established patches. The location of young and old populations in the studied system and altered gene flow because of increased population density and decreased inter-patch distances between extant populations may explain the observed lower genetic differentiation in the younger populations. This study exemplifies the importance of incorporating data on historical landscape changes in population genetic research at the landscape scale.

Age Factors↗
PubMed1991

The genetic structure of natural populations of Drosophila melanogaster. XXIV. Effects of hybrid dysgenesis on the components of genetic variance of variability.

Eight hundred second chromosomes were extracted from the Ishigakijima population, one of the southernmost populations of Drosophila melanogaster in Japan. Half of them were extracted in Native cytoplasm (P-type), and half in Foreign cytoplasm (M-type). Various population-genetic parameters, including the frequency of lethal-carrying second chromosomes (Q = 0.235 for the Native; 0.218 for the Foreign), the allelism rate of lethal second chromosome (Ic = 0.0217 for the Native; 0.0134 for the Foreign), the homozygous detrimental and lethal loads (D = 0.179 for the Native; 0.270 for the Foreign; L = 0.262 for the Native; 0.240 for the Foreign), the average degree of dominance of mildly deleterious mutations (ĥE = 0.244 for the Native; 0.208 for the Foreign), and the components of genetic variance for viability [additive (sigma A2) and dominance (sigma D2)](ŝigma A2 = 0.0187 for the Native; 0.0172 for the Foreign; ŝigma D2 = 0.0005 for the Native; 0.0009 for the Foreign) were estimated. The data indicate that D was significantly larger and hE was significantly smaller in the Foreign cytoplasm. However, the estimates of additive and dominance variances were not significantly different between the two cytoplasms. The additive genetic variance for viability in the Ishigakijima population was greater than expected on the basis of mutation-selection balance confirming previous studies on papers of D. melanogaster in warm climates.

Animals↗