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排序方式: 共有273条查询结果,搜索用时 15 毫秒
91.
Alomá Moreno O y MJ Freuler 《Phyton》2015,84(2):466-472
The present study of the Orchidaceae family was carried out in Guamuahaya’s mountain range, from 2000 to March 2013. Fifteen districts were explored after 33 expeditions in the Province of Cienfuegos. Ninety two plant species were identified in the studied area, taking into account the ecological parameters of the mountainous areas of Cienfuegos and Cumanayagua municipalities. 相似文献
92.
D F Wyszynski C T Baldwin M A Cleves Y Amirault V G Nolan J J Farrell A Bisbee A Kutlar L A Farrer M H Steinberg 《Cellular and molecular biology, including cyto-enzymology》2004,50(1):23-33
In patients with sickle cell anemia, fetal hemoglobin (HbF) concentrations vary by 2 orders of magnitude. This variance may be a result of heterogeneity in gene regulatory elements; accordingly, we searched for single nucleotide polymorphisms (SNPs) that might identify this variation. More than 180 SNPs were studied in 38 genes in 280 sickle cell anemia patients. The strongest association with HbF was found with SNPs near a QTL previously localized on chromosome 6q22.3-q23.2. Initially, two SNPs were identified in intergenic portions of this QTL and were associated with about a 20% difference in percent HbF. Subsequently, we genotyped 44 additional SNPs in the genomic region between 136.1 Mb and 137.5 Mb on chromosome 6q. Twelve SNPs, associated with a 20%-30% difference in HbF concentrations, were located in the introns of four genes, PDE7B, MAP7, MAP3K5 and PEX7. In K562 cells, the p38-MAPK pathway has been associated with the activation of gamma-globin gene expression by histone deacetylase inhibitors. Haplotypes C-T-T-T in MAP7 and T-C-C in PEX7 were significantly associated with increases in concentration of HbF, both showing strong dominance. Genetic elements abutting the 6q22.3-q23.2 QTL, may harbor trans-acting elements that help modulate baseline HbF level in sickle cell anemia. 相似文献
93.
Nicolas Helmstetter Aleksandra D Chybowska Christopher Delaney Alessandra Da Silva Dantas Hugh Gifford Theresa Wacker Carol Munro Adilia Warris Brian Jones Christina A Cuomo Duncan Wilson Gordon Ramage Rhys A Farrer 《Genetics》2022,221(1)
Candida glabrata is the second most common etiological cause of worldwide systemic candidiasis in adult patients. Genome analysis of 68 isolates from 8 hospitals across Scotland, together with 83 global isolates, revealed insights into the population genetics and evolution of C. glabrata. Clinical isolates of C. glabrata from across Scotland are highly genetically diverse, including at least 19 separate sequence types that have been recovered previously in globally diverse locations, and 1 newly discovered sequence type. Several sequence types had evidence for ancestral recombination, suggesting transmission between distinct geographical regions has coincided with genetic exchange arising in new clades. Three isolates were missing MATα1, potentially representing a second mating type. Signatures of positive selection were identified in every sequence type including enrichment for epithelial adhesins thought to facilitate fungal adhesin to human epithelial cells. In patent microevolution was identified from 7 sets of recurrent cases of candidiasis, revealing an enrichment for nonsynonymous and frameshift indels in cell surface proteins. Microevolution within patients also affected epithelial adhesins genes, and several genes involved in drug resistance including the ergosterol synthesis gene ERG4 and the echinocandin target FKS1/2, the latter coinciding with a marked drop in fluconazole minimum inhibitory concentration. In addition to nuclear genome diversity, the C. glabrata mitochondrial genome was particularly diverse, with reduced conserved sequence and conserved protein-encoding genes in all nonreference ST15 isolates. Together, this study highlights the genetic diversity within the C. glabrata population that may impact virulence and drug resistance, and 2 major mechanisms generating this diversity: microevolution and genetic exchange/recombination. 相似文献
94.
N6‐methyladenine is the most widespread mRNA modification. A subset of human box C/D snoRNA species have target GAC sequences that lead to formation of N6‐methyladenine at a key trans Hoogsteen‐sugar A·G base pair, of which half are methylated in vivo. The GAC target is conserved only in those that are methylated. Methylation prevents binding of the 15.5‐kDa protein and the induced folding of the RNA. Thus, the assembly of the box C/D snoRNP could in principle be regulated by RNA methylation at its critical first stage. Crystallography reveals that N6‐methylation of adenine prevents the formation of trans Hoogsteen‐sugar A·G base pairs, explaining why the box C/D RNA cannot adopt its kinked conformation. More generally, our data indicate that sheared A·G base pairs (but not Watson–Crick base pairs) are more susceptible to disruption by N6mA methylation and are therefore possible regulatory sites. The human signal recognition particle RNA and many related Alu retrotransposon RNA species are also methylated at N6 of an adenine that forms a sheared base pair with guanine and mediates a key tertiary interaction. 相似文献
95.
Intraspecific DNA sequence variation of the mitochondrial control region of white sturgeon (Acipenser transmontanus) 总被引:3,自引:0,他引:3
Intraspecific sequence variation in the D-loop region of mtDNA in white
sturgeon (Acipenser transmontanus), a relict North American fish species,
was examined in 27 individuals from populations of the Columbia and Fraser
rivers. Thirty-three varied nucleotide positions were present in a
462-nucleotide D-loop sequence, amplified using the polymerase chain
reaction. Bootstrapped neighbor-joining and maximum- parsimony trees of
sequences from 19 haplotypes suggest that the two populations have recently
diverged. This is consistent with the hypothesis that the Columbia River, a
Pleistocene refugium habitat, was the source of founders for the Fraser
River after the last glacial recession. On the basis of a divergence time
of 10-12 thousand years ago, the estimated substitution rate of the white
sturgeon D-loop region is 1.1-1.3 x 10(-7) nucleotides/site/year, which is
comparable to rates for hypervariable sequences in the human D-loop region.
Furthermore, the ratio of mean percent nucleotide differences in the D-
loop (2.27%) to that in whole mtDNA (0.54%, as estimated from
restriction-enzyme data) is 4.3, which is similar to the fourfold-to-
fivefold-higher substitution rate estimated for the human D-loop. The high
nucleotide substitution rate of the hypervariable region indicates that the
vertebrate D-loop has potential as a genetic marker in molecular population
studies.
相似文献
96.
Meiotic crossing-over in nondisjoined chromosomes of children with trisomy 21 and a congenital heart defect. 总被引:3,自引:0,他引:3 下载免费PDF全文
C M Howard G E Davies M J Farrer L M Cullen M M Coleman R Williamson R K Wyse R Palmer A M Kessling 《American journal of human genetics》1993,53(2):462-471
We have used DNA polymorphisms to study meiotic crossovers of chromosome 21q in 27 nuclear families. Each family had a child with Down syndrome and a congenital heart defect. Twenty DNA polymorphisms on chromosome 21 were used to determine parental and meiotic origin of nondisjunction and to identify crossovers. Twenty-four cases were of maternal origin, and three were of paternal origin. Twenty-two unequivocal crossover events were identified. Sixteen crossovers were observed in 22 chromosome pairs nondisjoining at the second meiotic division. Fifty percent of crossover events in MI nondisjunction are detectable by molecular genetic means. Thus, the results suggest that, in this sample, each nondisjoined chromosome 21 pair has been involved in at least one crossover event. 相似文献
97.
Ancient large-scale genome duplications: phylogenetic and linkage analyses shed light on chordate genome evolution 总被引:12,自引:4,他引:8
Pebusque MJ; Coulier F; Birnbaum D; Pontarotti P 《Molecular biology and evolution》1998,15(9):1145-1159
Paralogous genes from several families were found in four human chromosome
regions (4p16, 5q33-35, 8p12-21, and 10q24-26), suggesting that their
common ancestral region underwent several rounds of large- scale
duplication. Searches in the EMBL databases, followed by phylogenetic
analyses, showed that cognates (orthologs) of human duplicated genes can be
found in other vertebrates, including bony fishes. In contrast, within each
family, only one gene showing the same high degree of similarity with all
the duplicated mammalian genes was found in nonvertebrates (echinoderms,
insects, nematodes). This indicates that large-scale duplications occurred
after the echinoderms/chordates split and before the bony vertebrate
radiation. It has been suggested that two rounds of gene duplication
occurred in the vertebrate lineage after the separation of Amphioxus and
craniate (vertebrates + Myxini) ancestors. Before these duplications, the
genes that have led to the families of paralogous genes in vertebrates must
have been physically linked in the craniate ancestor. Linkage of some of
these genes can be found in the Drosophila melanogaster and Caenorhabditis
elegans genomes, suggesting that they were linked in the triploblast
Metazoa ancestor.
相似文献
98.
Evidence for major gene inheritance of Alzheimer disease in families of patients with and without apolipoprotein E epsilon 4. 总被引:2,自引:1,他引:1
V. S. Rao A. Cupples C. M. van Duijn A. Kurz R. C. Green H. Chui R. Duara S. A. Auerbach L. Volicer J. Wells C. van Broeckhoven J. H. Growdon J. L. Haines L. A. Farrer 《American journal of human genetics》1996,59(3):664-675
Apolipoprotein E (APOE) genotype is the single most important determinant to the common form of Alzheimer disease (AD) yet identified. Several studies show that family history of AD is not entirely accounted for by APOE genotype. Also, there is evidence for an interaction between APOE genotype and gender. We carried out a complex segregation analysis in 636 nuclear families of consecutively ascertained and rigorously diagnosed probands in the Multi-Institutional Research in Alzheimer Genetic Epidemiology study in order to derive models of disease transmission which account for the influences of APOE genotype of the proband and gender. In the total group of families, models postulating sporadic occurrence, no major gene effect, random environmental transmission, and Mendelian inheritance were rejected. Transmission of AD in families of probands with at least one epsilon 4 allele best fit a dominant model. Moreover, single gene inheritance best explained clustering of the disorder in families of probands lacking epsilon 4, but a more complex genetic model or multiple genetic models may ultimately account for risk in this group of families. Our results also suggest that susceptibility to AD differs between men and women regardless of the proband's APOE status. Assuming a dominant model, AD appears to be completely penetrant in women, whereas only 62%-65% of men with predisposing genotypes develop AD. However, parameter estimates from the arbitrary major gene model suggests that AD is expressed dominantly in women and additively in men. These observations, taken together with epidemiologic data, are consistent with the hypothesis of an interaction between genes and other biological factors affecting disease susceptibility. 相似文献
99.
Endogenous chloride channels of insect sf9 cells. Evidence for coordinated activity of small elementary channel units 总被引:1,自引:0,他引:1 下载免费PDF全文
EH Larsen SE Gabriei MJ Stutts J Fullton EM Price RC Boucher 《The Journal of general physiology》1996,107(6):695-714
The endogenous Cl- conductance of Spodoptera frugiperda (Sf9) cells was studied 20-35 h after plating out of either uninfected cells or cells infected by a baculovirus vector carrying the cloned beta-galactosidase gene (beta-Gal cells). With the cation Tris+ in the pipette and Na+ in the bath, the reversal potential of whole-cell currents was governed by the prevailing Cl- equilibrium potential and could be fitted by the Goldman-Hodgkin-Katz equation with similar permeabilities for uninfected and beta-Gal cells. In the frequency range 0.12 < f < 300 Hz, the power density spectrum of whole-cell Cl- currents could be fitted by three Lorentzians. Independent of membrane potential, >50% of the total variance of whole-cell current fluctuations was accounted for by the low frequency Lorentzian (fc = 0.40 +/- 0.03 Hz, n = 6). Single-Cl- channels showed complex gating kinetics with long lasting (seconds) openings interrupted by similar long closures. In the open state, channels exhibited fast burst-like closures. Since the patches normally contained more than a single channel, it was not possible to measure open and closed dwell-time distributions for comparing single-Cl- channel activity with the kinetic features of whole-cell currents. However, the power density spectrum of Cl- currents of cell-attached and excised outside-out patches contained both high and low frequency Lorentzian components, with the corner frequency of the slow component (fc = 0.40 +/- 0.02 Hz, n = 4) similar to that of whole-cell current fluctuations. Chloride channels exhibited multiple conductance states with similar Goldman-Hodgkin-Katz-type rectification. Single-channel permeabilities covered the range from approximately 0.6.10(-14) cm5/s to approximately 6.10(-14) cm3/s, corresponding to a limiting conductance (gamma 150/150) of approximately 3.5 pS and approximately 35 pS, respectively. All states reversed near the same membrane potential, and they exhibited similar halide ion selectivity, P1 > PCl approximately PBr. Accordingly, Cl- current amplitudes larger than current flow through the smallest channel unit resolved seem to result from simultaneous open/shut events of two or more channel units. 相似文献
100.
In vivo and in vitro processing of seed reserve protein in the endoplasmic reticulum: evidence for two glycosylation steps 总被引:12,自引:0,他引:12 下载免费PDF全文
Cotyledons of the common bean (Phaseolus vulgaris L.) synthesize large amounts of the reserve protein phaseolin. The polypeptides are synthesized on membrane-bound polysomes, pass through the endoplasmic reticulum (ER) and accumulate in protein bodies. For a study of the biosynthesis and processing of phaseolin, developing cotyledons were labeled with radioactive amino acids, glucosamine and mannose, and isolated fractions (polysomal RNA, polysomes, and rough ER) were used for in vitro protein synthesis. Newly synthesized phaseolin present in the ER of developing cotyledons can be fractioned into four glycopolypeptides by SDS PAGE. In vitro synthesis with polysomal RNA results in the formation of two polypeptides by polysome run-off shows that glycosylation is a co-translational event. The two unglycosylated polypeptides formed by polysome run-off are slightly smaller than the two polypeptides formed by in vitro translation of isolated RNA, indicating that a signal peptide may be present on these polypeptides. Run-off synthesis with rough ER produces a pattern of four polypeptides similar to the one obtained by in vivo labeling. The two abundant glycopolypeptides formed by polysome run-off. This result indicates the existence of a second glycosylation event for the abundant polypeptides. Inhibition of glycosylation by Triton X-100 during chain-completion with rough ER was used to show that these two glycosylation steps normally occur sequentially. Both glycosylation steps are inhibited by tunicamycin. Analysis of carhohydrate to protein ratios of the different polypeptides and of trypsin digests of polypeptides labeled with [(3)H]glucosamine confirmed the conclusion that some glycosylated polypeptides contain two oligosaccharide chains, while others contain only one. An analysis of tryptic peptide maps shows that each of the unglycosylated polypeptides is the precursor for one glycosylated polypeptide with one oligosaccharide chain and one with two oligosaccharide chains. 相似文献