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At least 1,099 records · Page 61Linked to original sources
PubMed1995

[Genetic structure and origin of the tetraploid toad Bufo danatensis Pisanetz, 1978 (Amphibia, Bufonidae) from Central Asia. Biochemical polymorphism and comparison of the level of heterozygosity of diploid species with tetraploid species].

Comparison of individual variation at 24 biochemical loci in members of the species complex of Palearctic green toads showed that the heterozygosity of the tetraploid species Bufo danatensis (Hobs + 0.45) was significantly higher than that of the diploid species B. viridis, B. sp., and B. raddei (Hobs = 0.009 - 0.103). Such difference can be explained only by a hybrid origin of the tetraploid species. Individual electrophoretic variability of the polyploid toad species is associated with an allelic variation that is manifested in constantly heterozygous spectra as the gene dosage effect. At the population level, this phenomenon found in Pamir toads is caused by irregular meiosis in founders of the population or by directional changes in gene regulation. Genotypic distributions in zones of contact of the diploid and tetraploid taxons demonstrate the possibility of restricted introgressive hybridization.

Animals↗
PubMed2000

Genetic structure and evolution of RAC-GTPases in Arabidopsis thaliana.

Rho GTPases regulate a number of important cellular functions in eukaryotes, such as organization of the cytoskeleton, stress-induced signal transduction, cell death, cell growth, and differentiation. We have conducted an extensive screening, characterization, and analysis of genes belonging to the Ras superfamily of GTPases in land plants (embryophyta) and found that the Rho family is composed mainly of proteins with homology to RAC-like proteins in terrestrial plants. Here we present the genomic and cDNA sequences of the RAC gene family from the plant Arabidopsis thaliana. On the basis of amino acid alignments and genomic structure comparison of the corresponding genes, the 11 encoded AtRAC proteins can be divided into two distinct groups of which one group apparently has evolved only in vascular plants. Our phylogenetic analysis suggests that the plant RAC genes underwent a rapid evolution and diversification prior to the emergence of the embryophyta, creating a group that is distinct from rac/cdc42 genes in other eukaryotes. In embryophyta, RAC genes have later undergone an expansion through numerous large gene duplications. Five of these RAC duplications in Arabidopsis thaliana are reported here. We also present an hypothesis suggesting that the characteristic RAC proteins in higher plants have evolved to compensate the loss of RAS proteins.

Amino Acid Sequence↗
PubMed1975

Fine genetic structure of the 2D3-2F5 region of the X-chromosome of Drosophila melanogaster.

97 lethal and semilethal mutations were induced by ethyl methanesulfonate, nitrosomethyl urea and gamma-irradiation in the 2D3-F5 region of the X-chromosome of D. melanogaster. Approximately 1 per cent of the tested X-chromosomes carried a lethal in the 2D3-2F5 region. The mutation frequencies per band or DNA content in the region and the whole X-chromosome are equal. Complementation analysis revealed at least 10 functionally independent essential loci in this region including about 10 bands. The data presented in this study support the one band--one gene hypothesis. The Pgd locus coding for 6-phosphogluconate dehydrogenase (6PGD) is mapped in the 2D3 (OR 2D4) band. Isolation of 11 lethal or semilethal point mutations with null or reduced 6PGD activity shows that the Pgd locus is a vital one.

Chromosome Mapping↗
PubMed2006

Contrasting genetic structures across two hybrid zones of a tropical reef fish, Acanthochromis polyacanthus (Bleeker 1855).

Hybrid zones are natural laboratories offering insights into speciation processes. Narrow hybrid zones are less common in the sea than on land consistent with higher dispersal among marine populations. Acanthochromis polyacanthus is an unusual bony marine fish with philopatric dispersal that exists as allopatric stocks of white, bicoloured and black fish on the Great Barrier Reef (GBR). At two latitudes, different morphs coexist and hybridize at narrow contact zones. Sequence data from mitochondrial Hypervariable Region 1 revealed contrasting patterns of introgression across these zones. At the northern hybrid zone, a single clade of mitochondrial haplotypes was found in all white fish, hybrids and tens of kilometres into pure bicoloured stock. At the southern hybrid zone, there was no introgression of mitochondrial genes into black fish and hybrids shared the bicoloured haplotypes. Based on this asymmetry, we postulate that black fish from the southern GBR have experienced a selective sweep of their mitochondrial genome, which has resulted in almost total reproductive isolation.

Animals↗
PubMed2002

Hierarchical analysis of genetic structure in Spanish donkey breeds using microsatellite markers.

The hierarchical population structure of five, native-Spanish donkey breeds (Andaluza, Catalana, Mallorquina, Encartaciones and Zamorano-Leonesa) has been studied using F-statistics. In addition, nine Moroccan asses and 24 Merens breed horses were included in the analysis. Data came from 15 DNA microsatellites. The analysis shows that Spanish donkeys are substructured at both hierarchical levels studied, among breeds and within breeds (between subpopulations). In the whole population, the deficit of heterozygotes was estimated to be about 21%. The fixation indices corresponding to differences between breeds, subpopulations within breeds, and within subpopulations were estimated to be 6.4%, 3.5% and 3.0%, respectively. The dendrogram obtained shows that the Andaluza and the Moroccan ass form a separate cluster from the northern Spanish breeds (Catalana, Encartaciones, Mallorquina and Zamorana-Leonesa). These groupings coincide with those obtained from historical and archaeological data.

Analysis of Variance↗
PubMed1980

[Patterns in the distribution of GPD- alleles in Azerbaijan. II. Population genetic structure of 3 villages in the Shekii district].

In order to clear out the role of genetico-automatic processes in Gd- distribution the investigation of population structure of three settlements in the Shekii district was carried out. Sex and age ratios and the average number of living children on one marriage (> 5.7) bear evidence of expanded reproduction in this population. The high frequency of endogamous marriages (approximately 80%) and 14 cases of consaguinous marriage for 183 analysed pedigree were revealed. The allele frequencies in 6 polymorphic systems were determined: ABO, Rh, Hp, PGM, Gc and AP; in the first three there were found out the statistically significant differences in alleles' frequency between subpopulations, but not in the last three systems. The differentiation type of allele frequency in all 6 loci was similar in subpopulations. The inbreeding coefficient fst determined upon the differentiation of the gene frequency at three loci is 0.00583.

Adolescent↗
PubMed1980

Genetic structure of avian myeloblastosis virus, released from transformed myeloblasts as a defective virus particle.

Chicken myeloblasts transformed by avian myeloblastosis virus (AMV) in the absence of nondefective helper virus (termed nonproducer cells) were found to release a defective virus particle (DVP) that contains avian tumor viral gag proteins but lacks envelope glycoprotein and a DNA polymerase. Nonproducer cells contain a Pr76 gag precursor protein and also a protein that is indistinguishable from the Pr180 gag-pol protein of nondefective viruses. The RNA of the DVP is 7.5 kilobases (kb) long and is 0.7 kb shorter than the 8.2-kb RNAs of the helper viruses of AMV, MAV-1 and MAV-2. Comparisons based on RNA.cDNA hybridization and mapping of RNase T1-resistant oligonucleotides indicated that DVP RNA shares with MAV RNAs nearly isogenic 5'-terminal gag and pol-related sequences of 5.3 kb and a 3'-terminal c-region of 0.7 kb that is different from that found in other avian tumor viruses. Adjacent to the c-region, DVP RNA contains a contiguous specific sequence of 1.5 kb defined by 14 specific oligonucleotides. Except for two of these oligonucleotides that map at its 5' end, this sequence is unrelated to any sequences of nondefective avian tumor viruses of four different envelope subgroups as well as to the specific sequences of fibroblast-transforming avian acute leukemia and sarcoma viruses of four different RNA subgroups. The specific sequence of the DVP RNA is present in infectious stocks of AMV from this and other laboratories in an AMV-transformed myeloblast line from another laboratory, and it is about 70% related to nucleotide sequences of E26 virus, an independent isolate of an AMV-like virus. Preliminary experiments show DVP to be leukemogenic if fused into susceptible cells in the presence of helper virus. We conclude that DVP RNA is the leukemogenic component of infectious AMV and that its specific sequence, termed AMV, may carry genetic information for oncogenicity. Thus we have found here a transformation-specific RNA sequence, unrelated to helper virus, in a highly oncogenic virus that does not transform fibroblasts.

Animals↗
PubMed1998

Genetic structure of IDDM1: two separate regions in the major histocompatibility complex contribute to susceptibility or protection. Belgian Diabetes Registry.

We analyzed 11 markers in the IDDM1 region in 120 IDDM patients and 83 healthy control subjects who were fully matched for the highest risk HLA-DQA1*0301-DQB1 *0302/DQA1*0501-DQB1*0201 genotype. Our study provides strong evidence that two regions in the major histocompatibility complex contribute to IDDM susceptibility or protection. First, despite selection for highest IDDM-associated risk DQ genotypes, this region displays extensive linkage disequilibrium (LD) differences between IDDM patients and control subjects. A second critical region was mapped around the microsatellite locus D6S273 centromeric of TNF, and it is approximately 200 kb in size. LD analysis shows that "diabetogenic haplotypes" may have resulted from a recombination telomeric of D6S1014 in the region of D6S273 and TNFa. Haplotype analysis using HLA and microsatellite loci refines IDDM risk assessment in carriers of the HLA-DQ highest risk genotype.

Adult↗
PubMed2006

Mating-type genes and the genetic structure of a world-wide collection of the tomato pathogen Cladosporium fulvum.

Two mating-type genes, designated MAT1-1-1 and MAT1-2-1, were cloned and sequenced from the presumed asexual ascomycete Cladosporium fulvum (syn. Passalora fulva). The encoded products are highly homologous to mating-type proteins from members of the Mycosphaerellaceae, such as Mycosphaerella graminicola and Cercospora beticola. In addition, the two MAT idiomorphs of C. fulvum showed regions of homology and each contained one additional putative ORF without significant similarity to known sequences. The distribution of the two mating-type genes in a world-wide collection of 86 C. fulvum strains showed a departure from a 1:1 ratio (chi(2)=4.81, df=1). AFLP analysis revealed a high level of genotypic diversity, while strains of the fungus were identified with similar virulence spectra but distinct AFLP patterns and opposite mating-types. These features could suggest the occurrence of recombination in C. fulvum.

Amino Acid Sequence↗
PubMed1993

Genetic structure of natural populations of Dryas iulia (Lepidoptera: Nymphalidae) revealed by enzyme polymorphism and mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP).

Dryas iulia appears to have undergone a mode of evolution different from that of other members of its subfamily (Heliconiinae). While other species constitute highly subdivided and inbred populations, those of D. iulia are thought to be large and uniform. Analyzing six samples from Southern Brazil (state of Rio Grande do Sul) in relation to three enzyme systems (EST, LAP, and PGM) and their mtDNA RFLP patterns, we found that they are very similar at the molecular level. The F statistics for enzyme polymorphism data revealed that inbreeding makes a great contribution to the population homozygosity, since FIS equals 0.1322 and FST equals 0.0023. Since the chi-square test showed that FST is not significant, we conclude that all localities belong to the same population. The mtDNA differentiation was about 12 times greater than for nuclear genes; FST was equivalent to 0.0265. We suggest that this difference is due to a higher dispersal of males, in relation to females.

Animals↗
PubMed2004

Patterns of DNA sequence diversity and genetic structure after a range expansion: lessons from the infinite-island model.

It has been long recognized that population demographic expansions lead to distinctive features in the molecular diversity of populations. However, recent simulation results have suggested that a distinction could be made between a pure demographic expansion in an unsubdivided population, and a range expansion in a subdivided population, both leading to a large increase in the total number of the individuals. In order to better characterize the effect of a range expansion, I introduce a simple model of instantaneous expansion under an infinite-island model, under which I derive the distribution of the number of mutation differences between pairs of genes (the mismatch distribution), the heterozygosity, the average number of pairwise difference, and the fixation index F(ST). These derivations are checked against simulations, and are shown to lead to results qualitatively similar to those one would obtain after a range expansion in a 2-dimensional stepping-stone model. I then apply these results to estimate immigration rates in hunter-gather and post-Neolithic human populations from patterns of mitochondrial (mtDNA) diversity. Potential problems with this estimation procedure are also discussed.

Computer Simulation↗
PubMedDate not supplied

[The effect of chronic exposure to cadmium and gamma radiation at low doses on the genetic structures in mice].

The DNA-protein cross-links (DPC) in mouse thymocytes and spleen lymphocytes, the number of abnormal sperm heads (ASH) and the number of micronuclei (MN) in normochromatic erythrocytes (NCE) of peripheral blood were studied in mice exposed to long-term low-intensity gamma radiation (0.072 cGy/days) and/or cadmium with drinking water (0.01 mg Cd2+/l) for 20, 40 and 80 days. The dependence of DPC level on the total dose (exposure time) of gamma radiation and/or cadmium is nonlinear. The maximal level of DPC in cells of lymphoid organs upon exposure to gamma radiation or cadmium was recorded on the 40-th day, and under combined exposure on the 20-th day of the experiment. The long-term exposure to cadmium or gamma radiation causes an increase in the ASH frequency. The increase in frequencies of MN in NCE and reciprocal translocations in spermatocytes was not found.

Animals↗
PubMed1997

Genetic structure and chromosomal mapping of MyD88.

The myeloid differentiation (MyD) marker MyD88 was initially characterized as a primary response gene, upregulated in mouse M1 myeloleukemic cells in response to differentiation induced by interleukin-6. Subsequent analysis revealed that MyD88 possesses a unique modular structure, which consists of an N-terminal "death domain," similar to the intracellular segments of TNF receptor 1 and Fas, and a C-terminal region related to the cytoplasmic domains of the Drosophila morphogen Toll and vertebrate interleukin-1 receptors. In this report we describe the cloning and gene structure of mouse MyD88. The complete coding sequence of mouse MyD88 spans five exons, with the first exon encoding the complete death domain. Zooblot analysis revealed that MyD88 is an evolutionarily conserved gene. MyD88 was localized to the distal region of mouse chromosome 9 by interspecific backcross mapping. The human homolog (hMyD88) was mapped to chromosome 3p22-p21.3 by PCR analysis of a human chromosome 3 somatic cell hybrid mapping panel. Northern blot analysis revealed widespread expression of MyD88 in many adult mouse tissues, and RT-PCR studies detected MyD88 mRNA in T and B cell lines and differentiating embryonic stem cells. The broad expression pattern demonstrates that mouse MyD88 expression is not restricted to cells of myeloid lineage as was originally believed.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

The genetic structure of English villages: surname diversity changes between 1976 and 1997.

OBJECTIVE: To examine the change in the coefficient of relationship by isonymy (Ri) over a 21-year period. RESEARCH DESIGN: Ri was calculated from the surnames of males in the registers of electors for 15 villages near Oxford in 1976 and again in 1997. The within-residence component reflected the number of adult men of the same surname resident at the same address while the between-resident component of Ri was calculated by counting only one name of any surname at each address listed in the registers. RESULTS: Ri tended to decrease during the 21-year-period in 14 of the 15 villages and the between-resident component of Ri also tended to decrease in 14 of the villages. The within-residence component decreased in a statistically non-significant proportion (11 of the 15 villages). CONCLUSIONS: This study, in keeping with some but not all other surveys, showed that there was a tendency for random isonymy to decline in the 20th century. The reduction in the between-residence component can be accounted for by migration into the villages.

Adult↗
PubMed1991

[Genetic structure of the Mongols as derived from the ABO, MN, Rh, EsD, GLO1, PGM1, AcP, 6-PGD, Hp, Gc, Tf, C'3 and ChE2 loci].

According to integral characterization of gene frequencies of the investigated loci AB0, MN, Rh, GLO1, PGM1, EsD, AcP, 6-PGD, Hp, Tf, Gc, C'3 and ChE2, Mongolian population has high level of polymorphism, with the exception of haplotypes R" (cdE) and Ry(CdE) at the Rh locus and TfB0-1 at the Tf locus. The data on biochemical and immunological polymorphic gene markers analysed in the population of Mongolia show that the Mongolians have some distinctive features, in comparison with the mean-in-the-world characteristics: high frequencies of the B genes at the AB0 locus; D, E, R1 and R2 at the Rh locus; GLO11, PGDc, TfDChi, E2(C5+), PGM1(1+); low frequencies of the genes A(AB0), R0(Rh), AcPc, Hp1, Gc2, C'3F, PGM 1(2-); the rest of the genes at the above-mentioned loci and the genes of the locus MN have the mean-in-the-world frequencies.

ABO Blood-Group System↗
PubMed2003

Historical demography and genetic structure of sister species: deermice (Peromyscus) in the North American temperate rain forest.

To investigate the evolutionary and biogeographical history of Peromyscus keeni and P. maniculatus within the coastal forest ecosystem of the Pacific Northwest of North America, we sampled 128 individuals from 43 localities from southeastern Alaska through Oregon. We analysed mitochondrial DNA variation using DNA sequence data from the mitochondrial cytochrome-b (cyt-b) gene and control region, and we found two distinct clades consistent with the morphological designation of the two species. The sequence divergence between the two clades was 0.0484 substitutions per site for cyt-b and 0.0396 for the control region, suggesting that divergence of the two clades occurred during the middle to late Pleistocene. We also examined the historical demography of the two clades using stepwise and exponential expansion models, both of which indicated recent rapid population growth. Furthermore, using the program migrate we found evidence of migration from populations north of the Fraser River (British Columbia) to the south in both clades. This study demonstrates the utility of these model-based demographic methods in illuminating the evolutionary and biogegographic history of natural systems.

Animals↗
PubMed2006

Merino sheep breed's genetic resistance to scrapie: genetic structure and comparison of five eradication strategies.

Three thousand one hundred and ninety-three Merino-breeding males were genotyped for Scrapie-resistance gene. They showed a high frequency of ARQ allele while VRQ allele frequency, linked to the highest susceptibility, was close to 0. Alleles linked to Scrapie-susceptibility frequencies have been studied in different Merino flocks. Most of the variability is intraflock, not interflock. In addition, there is an excess of heterozygotes due to crossbreeding or Wahlund effect. Five control and prevention strategies were studied: first genotyping males and females and eliminating VRQ carriers and ARQ/ARQ rams; second genotyping males and females and eliminating VRQ carriers; third genotyping males and eliminating VRQ carriers and ARQ/ARQ rams; fourth genotyping males and using only as breeders ARR/ARR, ARR/AHQ, AHQ/AHQ and ARQ/ARQ rams; fifth genotyping males and using only as breeders ARR/ARR, ARR/AHQ and AHQ/AHQ rams. They were simulated from allelic and genotypic frequencies to decide which animals had to be genotyped and which animals had to be eliminated due to their genotypes and risk levels. The third option, to genotype rams and to eliminate ARQ/ARQ and VRQ carriers, would be the best strategy to improve the resistance and would cause minimal cost and loss of animals.

Animals↗
PubMed2004

Fine-scale genetic structure and gene dispersal in Centaurea corymbosa (Asteraceae) I. Pattern of pollen dispersal.

Pollen dispersal was characterized within a population of the narrowly endemic perennial herb, Centaurea corymbosa, using exclusion-based and likelihood-based paternity analyses carried out on microsatellite data. Data were used to fit a model of pollen dispersal and to estimate the rates of pollen flow and mutation/genotyping error, by developing a new method. Selfing was rare (1.6%). Pollen dispersed isotropically around each flowering plant following a leptokurtic distribution, with 50% of mating pairs separated by less than 11 m, but 22% by more than 40 m. Estimates of pollen flow lacked precision (0-25%), partially because mutations and/or genotyping errors (0.03-1%) could also explain the occurrence of offspring without a compatible candidate father. However, the pollen pool that fertilized these offspring was little differentiated from the adults of the population whereas strongly differentiated from the other populations, suggesting that pollen flow rate among populations was low. Our results suggest that pollen dispersal is too extended to allow differentiation by local adaptation within a population. However, among populations, gene flow might be low enough for such processes to occur.

Centaurea↗