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91.
Castagnone-Sereno P; Semblat JP; Leroy F; Abad P 《Molecular biology and evolution》1998,15(9):1115-1122
A highly abundant satellite DNA comprising 20% of the Meloidogyne fallax
(Nematoda, Tylenchida) genome was cloned and sequenced. The satellite
monomer is 173 bp long and has a high A + T content of 72.3%, with frequent
runs of A's and T's. The sequence variability of the monomers is 2.7%,
mainly due to random distribution of single-point mutations. A search for
evidence of internal repeated subunits in the monomer sequence revealed a
6-bp motif (AAATTT) for which five degenerated repeats, differing by just a
single base pair, could be identified. Pairwise comparison of the M. fallax
satellite with those from the sympatric species Meloidogyne chitwoodi and
Meloidogyne hapla revealed a high sequence similarity (68.39%) with one
satellite DNA subfamily in M. chitwoodi, which indicated an unexpected
close relationship between them. Given the high copy number and the extreme
sequence homogeneity among monomeric units, it may be assumed that the
satellite DNA of M. fallax could have evolved through some recent and
extensive amplification burst in the nematode genome. In this case, its
relatively short life would not yet have allowed the accumulation of random
mutations in independent amplified repeats. Considering the morphological
resemblance between the two species and their ability to produce
interspecific fertile hybrids under controlled conditions, these results
indicate that M. fallax may share a common ancestor with M. chitwoodi, from
which it could have diverged recently. All these data suggest that M.
fallax could be the result of a recent speciation process and show that
Meloidogyne satellite DNAs may be of interest to resolve phylogenetic
relationships among closely related species from this genus.
相似文献
92.
Cytochrome b, flavins, and ubiquinone-50 in enucleated human neutrophils (polymorphonuclear leukocyte cytoplasts) 总被引:1,自引:0,他引:1
R Lutter R van Zwieten R S Weening M N Hamers D Roos 《The Journal of biological chemistry》1984,259(15):9603-9606
Neutrophilic granulocytes contain an oxidase system in their plasma membrane that can be activated to generate superoxide radicals and hydrogen peroxide. Cytochrome b, flavoprotein, and ubiquinone-50 have been proposed as components of this oxidase system. These components have been quantitated, but the results are obscured by different isolation procedures for plasma membranes from resting and activated neutrophils. This problem has now been avoided by the use of enucleated neutrophils (polymorphonuclear leukocyte cytoplasts), which are almost completely devoid of intracellular structures but contain an intact, activatable oxidase system (Roos, D., Voetman, A.A., and Meerhof, L.J. (1983) J. Cell Biol. 97, 368-377). Membranes of resting and phorbol myristate acetate-stimulated cytoplasts contain equal amounts of cytochrome b (4 pmol/milliunit of alkaline phosphatase) and also equal amounts of noncovalently bound FAD (2 pmol/milliunit of alkaline phosphatase). These findings refute the hypothesis that incorporation of cytochrome b and/or a flavoprotein into the plasma membrane constitutes the mechanism of activation of the oxidase system. Ubiquinone-50 is present neither in intact neutrophils nor in cytoplasts, excluding a role for this compound in the generation of bactericidal oxygen species by neutrophils. 相似文献
93.
Summary The -galactosidases in normal man-Chinese hamster somatic cell hybrids were investigated with antibodies specific for human -galactosidase A and antibodies specific for Chinese hamster -galactosidase. It was found that an isoenzyme in hybrid cells, which has an electrophoretic mobility between that of human -galactosidase A and Chinese hamster -galactosidase, contains immunologic determinants of both human and Chinese hamster origin, suggesting that it is a heteropolymeric molecule. Moreover, the locus for human -galactosidase, which was found to be X-linked, is the locus coding for -galactosidase A. Hybrids isolated after fusion of Chinese hamster cells with cells of a patient with Fabry's disease did not express human -galactosidase A or the heteropolymeric molecule even in the presence of the active human X chromosome, indicating that the deficiency of -galactosidase A in Fabry's disease is probably due to a mutation in a structural gene resulting in the inability to form immunologically detectable and functionally active molecules of -galactosidase A. 相似文献
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95.
Six new IgM allotypes-Msl6, Msl7, Ms21, Ms23, Ms24, and Ms25-have been detected. Genetics of these markers has been studied by radioimmunoassay, since immunodiffusion in gel was not sensitive enough to detect low concentrations of IgM in the serum. All the six markers are closely linked to thea locus; Ms 16 and Ms 17 behave as alleles and can be found associated with any of the three majora locus markers. In contrast to these findings, the other four allotypes are always associated with haplotypes carrying a particular a-locus marker associated with a particular chain allotype (Ms 16 or Ms 17). 相似文献
96.
Tim?Lu Christine?M?Costello Peter?JP?Croucher Robert?H?sler Günther?Deuschl Stefan?SchreiberEmail author 《BMC bioinformatics》2005,6(1):37
Background
Normalization is the process of removing non-biological sources of variation between array experiments. Recent investigations of data in gene expression databases for varying organisms and tissues have shown that the majority of expressed genes exhibit a power-law distribution with an exponent close to -1 (i.e. obey Zipf's law). Based on the observation that our single channel and two channel microarray data sets also followed a power-law distribution, we were motivated to develop a normalization method based on this law, and examine how it compares with existing published techniques. A computationally simple and intuitively appealing technique based on this observation is presented. 相似文献97.
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