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Query: UNIPROT:P06889 (Mol)
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Recent development of DNA markers provides powerful tools for population genetic analyses. Amplified fragment length polymorphism (AFLP) markers result from a polymerase chain reaction (PCR)-based DNA fingerprinting technique that can detect multiple restriction fragments in a single polyacrylamide gel, and thus are potentially useful for population genetic studies. Because AFLP markers have to be analysed as dominant loci in order to estimate population genetic diversity and genetic structure parameters, one must assume that dominant (amplified) alleles are identical in state, recessive (unamplified) alleles are identical in state, AFLP fragments segregate according to Mendelian expectations and that the genotypes of an AFLP locus are in Hardy-Weinberg equilibrium (HWE). The HWE assumption is untestable for natural populations using dominant markers. Restriction fragment length polymorphism (RFLP) markers segregate as codominant alleles, and can therefore be used to test the HWE assumption that is critical for analysing AFLP data. This study examined whether the dominant AFLP markers could provide accurate estimates of genetic variability for the Aedes aegypti mosquito populations of Trinidad, West Indies, by comparing genetic structure parameters using AFLP and RFLP markers. For AFLP markers, we tested a total of five primer combinations and scored 137 putative loci. For RFLP, we examined a total of eight mapped markers that provide a broad coverage of mosquito genome. The estimated average heterozygosity with AFLP markers was similar among the populations (0.39), and the observed average heterozygosity with RFLP markers varied from 0.44 to 0.58. The average FST (standardized among-population genetic variance) estimates were 0.033 for AFLP and 0.063 for RFLP markers. The genotypes at several RFLP loci were not in HWE, suggesting that the assumption critical for analysing AFLP data was invalid for some loci of the mosquito populations in Trinidad. Therefore, the results suggest that, compared with dominant molecular markers, codominant DNA markers provide better estimates of population genetic variability, and offer more statistical power for detecting population genetic structure.
Mol Ecol 1999 Jun
PMID:Population genetics of the yellow fever mosquito in Trinidad: comparisons of amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism (RFLP) markers. 1043 16

Activin uptake into Xenopus oocytes was studied by several complementary methods. Immunocytochemistry of adult ovary localized activin and follistatin in the cytoplasm of vitellogenic oocytes and surrounding follicle cells. Surface plasmon resonance analysis of protein interaction kinetics indicated that while follistatin or a complex of activin-follistatin bound to yolk vitellogenin, activin alone did not. Radioactive tracer analysis measured specific incorporation of activin by viable oocytes in vitro. Together, the results suggest that vitellogenic oocytes can import activins from follicle cells and that follistatin may act as a chaperone for binding activin to vitellogenin in yolk platelets.
Cell Mol Biol (Noisy-le-grand) 1999 Jul
PMID:Activin incorporation into vitellogenic oocytes of Xenopus laevis. 1051 87

We compare the performance of Nm estimates based on FST and RST obtained from microsatellite data using simulations of the stepwise mutation model with range constraints in allele size classes. The results of the simulations suggest that the use of microsatellite loci can lead to serious overestimations of Nm, particularly when population sizes are large (N > 5000) and range constraints are high (K < 20). The simulations also indicate that, when population sizes are small (N </= 500) and migration rates are moderate (Nm approximately 2), violations to the assumption used to derive the Nm estimators lead to biased results. Under ideal conditions, i.e. large sample sizes (ns >/= 50) and many loci (nl >/= 20), RST performs better than FST for most of the parameter space. However, FST-based estimates are always better than RST when sample sizes are moderate or small (ns </= 10) and the number of loci scored is low (nl < 20). These are the conditions under which many real investigations are carried out and therefore we conclude that in many cases the most conservative approach is to use FST.
Mol Ecol 1999 Sep
PMID:A comparison of two indirect methods for estimating average levels of gene flow using microsatellite data. 1056 57

A rare episode of regeneration of aspen (Populus tremuloides Michx.) by seeds occurred in Yellowstone National Park (YNP), Wyoming, USA, following extensive fires that occurred in 1988. In 1997, we sampled 410 aspen seedlings from 23 local populations distributed widely across YNP to determine how genetic diversity varies with elevation, substrate, plant competition, ungulate browsing, and geographical location. We employed 132 randomly amplified polymorphic DNA (RAPD) markers based on six primers to show genetic relationships within and among the postfire aspen seedling populations. Measures of genetic variation, including estimates of percentage polymorphic loci, expected heterozygosity, and Nei's FST, indicated that most of the variation occurred within rather than among local populations. There was no indication of geographical differentiation among sampled populations based on hierarchal estimates of Nei's FST, neighbour-joining, or correlations between genetic distance and geographical distance. Even genetically distant populations shared nearly 90% of the same markers. Within plots, the amount of genetic variation decreased slightly in response to increased percentage vegetative cover, mean seedling basal diameter, and mean seedling height. Geological substrate, density of lodgepole pine (Pinus contorta var. latifolia Dougl.) seedlings, browsing intensity, and elevation were not significantly related to levels of genetic variation within the seedling plots. These data suggest that genetic variation and geographical structure among seedling populations may occur over time as the transition from seedling-dominated stands to clone-dominated stands occurs.
Mol Ecol 1999 Nov
PMID:Genetic variation in postfire aspen seedlings in yellowstone national park 1062 Feb 21

The genetic subdivision of the endemic minnow, Zacco pachycephalus, in 12 rivers of Taiwan was studied by allozyme electrophoresis. Among 26 loci surveyed, six were significantly differentiated among sites. Allozyme genotype frequencies within samples accord with Hardy-Weinberg expectations. A highly divergent genetic structure among sites (FST = 0.497) with low genetic variability within samples (H = 0.006-0.062, mean = 0.03) suggests that local populations originated from a small number of founders. UPGMA and Fitch trees derived from Nei's genetic distance and hierarchical analysis of FST values reveal that samples of Z. pachycephalus can be divided into northern, middle, and southern subgroups and that most genetic variation (87%) is distributed among rather than within groups. It is proposed that there were two isolated refugia during the most recent glacial period, and that populations of the southern group (Group I) originated from a southern refugium in Taiwan below the boundary of the Kaoping River, and other groups (Group II), including northern and middle subgroups, originated from a refugium located on the extinct land-bridge between Taiwan and mainland China. The postglacial division between northern and middle subgroups may be due to hydrological differences between these two regions.
Mol Ecol 1999 Nov
PMID:Influence of glaciation on divergence patterns of the endemic minnow, Zacco pachycephalus, in Taiwan. 1062 Feb 31

We report here the sequence of a novel cDNA clone (FST, female-specific transcript), isolated by differential screening during a search for sexually mature accessory gland-specific transcripts from the medfly Ceratitis capitata. It contains an open reading frame (ORF) with a potential translational start site encoding a putative precursor peptide of 100 amino acids. The FST gene is expressed only in the female reproductive accessory glands. Like the accessory gland-specific antibacterial peptides ceratotoxins, its expression reaches the maximum level when sexual maturity is achieved. However, in contrast to ceratotoxins, it is expressed at a basal level in newly emerged females, and its expression does not increase after mating.
Insect Mol Biol 1999 Nov
PMID:FST, a female-specific transcript from the medfly Ceratitis capitata (Diptera: Tephritidae). 1063 72

To make inferences about the glacial refugia that harboured the limber pine, Pinus flexilis James, we examined the range-wide population structure of mitochondrial DNA (mtDNA) with eight size variants in the second intron of nad1. The data consisted of haplotypes from 704 trees collected from 40 localities. The value of FST for these populations was 0.80, which is a much larger value than has been reported for allozymes and chloroplast DNA (cpDNA) in limber pine, and it suggests that the number of seeds moving among localities per generation is approximately 0.12. Gene flow of this magnitude would allow mutation and subsequent genetic drift to have a substantial impact on the population structure of mtDNA. The majority of the mtDNA haplotypes are restricted to minor portions of the geographical range. The data are consistent with mtDNA differentiation in seven glacial refugia, followed by dispersal out of those refugia.
Mol Ecol 2000 Jan
PMID:Glacial refugia of limber pine (Pinus flexilis James) inferred from the population structure of mitochondrial DNA. 1065 78

The nest and population genetic structures of the Argentine ant, Linepithema humile were investigated using eight microsatellite loci. Genotypes of the sperm from spermathecae of 87 queens were consistent with all queens being singly inseminated. The probability of a double mating remaining undetected was low (0.012) suggesting that no queens or only a very low proportion mate multiply. The relatedness between the queens and their mates was negative (R = -0.164 +/- 0.044) and significantly different to zero (P = 0.020). However, the high negative relatedness value was caused by a significant allele frequency difference between the sexes at a single locus (Lhum-28). When this locus was removed from the analyses, the relatedness was not significantly different from zero (R = 0.013 +/- 0.050, P = 0.812). Analysis of 10 nests revealed that the genetic differentiation among nests was weak (FST = 0.003) and not distinguishable from zero (P = 0.468). Similarly, the overall relatedness among nestmate females was not significantly different from zero (R = 0.007 +/- 0.018, P = 0.706). These results are consistent with the lack of distinct nest boundaries and the large number of queens per nest in the population studied. Although mating takes place inside the nest, the inbreeding coefficient was close to zero (F = 0.007 +/- 0.025, P = 0.786). Overall, these data indicate substantial local gene flow mediated by movement of reproductives among colonies.
Mol Ecol 2000 Feb
PMID:Mating frequency and genetic structure of the Argentine ant Linepithema humile. 1067 56

Inhibin A and B are dimeric proteins capable of suppressing FSH both in vitro and in vivo. The principal form in the male is inhibin B which is produced in the testis and circulates to inhibit pituitary FSH secretion. Activin A, B and AB are dimeric proteins that share the same beta subunits with the inhibins but, in contrast, stimulate FSH secretion. Although activin A circulates, castration does not lead to a decrease in serum concentrations, indicating that the testis is not the major source of activin A. In the circulation, the activins are bound to a structurally unrelated binding protein, follistatin, that neutralizes the biological actions of these proteins. The subunits of the inhibins/activins as well as follistatin are also produced locally within the pituitary and their levels can be modulated by testosterone and gonadotrophin releasing hormone as well as by autocrine mechanisms. Consequently, the output of FSH is dependent of the balance between local processes and the circulating feedback exerted by testosterone and inhibin. There is increasing data to support the local gonadal production of not only inhibin but also activin and follistatin by both germ cells and somatic cells such as the Sertoli cells. Evidence is accumulating to support the concept that these proteins exert local regulatory mechanisms in the testis.
Mol Cell Endocrinol 2000 Mar 30
PMID:The roles of inhibin and related peptides in gonadal function. 1077 90

Amplified fragment length polymorphisms (AFLPs) were used to characterize the genetic diversity within and among natural populations of Sticherus flabellatus. Eight populations within the Sydney region of New South Wales, Australia were surveyed using 11 primer combinations. A total of 1108 reproducible bands were detected of which 469 (42%) were polymorphic. FST estimates averaged over all polymorphic loci indicated that significant genomic differentiation occurs among populations (average = 0.783). Genetic diversity within populations was assessed according to average heterozygosity (H) and percentage polymorphic loci (P) per population. Within-population diversity ranged from H = 0.12 and P = 33.69 to H = 0.04 and P = 15.99. Analysis of genetic similarity among populations suggested that the eight populations studied fall into two groups of four populations, based on population size and the condition of the habitat. Phenetic analysis (AMOVA) indicated that genetic variation is greater among populations (74.34%) than within populations (25.66%). These findings suggest that the breeding system of S. flabellatus is predominantly inbreeding, with genetic diversity maintained by occasional outcrossing in larger populations. The results presented in this study could provide evidence to support the proposal to protect natural stands of S. flabellatus, which has implications for the Australian horticulture industry.
Mol Ecol 2000 May
PMID:An analysis of genetic variation in natural populations of Sticherus flabellatus [R. Br. (St John)] using amplified fragment length polymorphism (AFLP) markers. 1079


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