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91.
92.
Summary The fidelity of mitotic chromosome transmission in Schizosaccharomyces pombe was estimated quantitatively by using cycloheximide resistance as a means to select cells that had undergone chromosome loss or nondisjunction. We aimed to investigate the connection between recombination and mitotic chromosome stability. A number of mutants defective in mitotic recombination such as cdc17-L16, rec59-72, and rec50-25 were tested and in these an approximately ten fold elevation of mitotic haploidization rate was found compared with controls. Our data suggest that recombination is important in controlling the maintenance of chromosomes during mitosis. 相似文献
93.
M26 Recombinational Hotspot and Physical Conversion Tract Analysis in the Ade6 Gene of Schizosaccharomyces Pombe 总被引:3,自引:1,他引:3 下载免费PDF全文
At the ade6 locus of Schizosaccharomyces pombe flanking markers have been introduced as well as five silent restriction site polymorphisms: four in the 5' upstream region and one in the middle of the gene. The mutations ade6-706, ade6-M26 (both at the 5' end) and ade6-51 (middle of the gene) were used as partners for crosses with the 3' mutation ade6-469. From these three types of crosses, wild-type recombinants were selected and analyzed genetically to assess association with crossing-over and physically to determine conversion tract lengths. The introduced restriction site polymorphisms (five vs. only one) neither influenced the pattern of recombinant types nor the distribution of conversion tracts. The hotspot mutation M26 enhances crossing-over and conversion to the same proportion. M26 not only stimulates conversion at the 5' end, but does this also (to a lower extent) at the 3' end of ade6 at a distance of more than 1 kb. The majority of meiotic conversion tracts are continuous and postmeiotic segregation of polymorphic sites is rare. Conversion tracts are slightly shorter with M26 in comparison with its control 706. The mean minimal length of tracts varies from 670 bp (M26) to 890 bp (706) to 1290 bp (51). It is concluded that M26 acts as an initiation site of recombination or enhances initiation of recombination. M26 does not act by termination of conversion. A region of recombination initiation exists at the 5' end of the ade6 gene also in the absence of the ade6-M26 hotspot mutation. 相似文献
94.
Harminder Pal Singh Daizy R. Batish Ravinder Kumar Kohli Komal Arora 《Plant Growth Regulation》2007,53(1):65-73
Arsenic (As) toxicity and its biochemical effects have been mostly evaluated in ferns and a few higher plants. In this study,
we investigated the effect of As (10.0 and 50.0 μM) on seedling growth, root anatomy, lipid peroxidation (malondialdehyde
and conjugated dienes), electrolyte leakage, H2O2 content, root oxidizability and the activities of antioxidant enzymes in mung bean (Phaseolus aureus Roxb.). Arsenic significantly enhanced lipid peroxidation (by 52% at 50.0 μM As), electrolyte leakage and oxidizability in
roots. However, there was no significant change in H2O2 content. Arsenic toxicity was associated with an increase in the activities of superoxide dismutase (SOD), guaiacol peroxidase
(GPX) and glutathione reductase (GR). In response to 50.0 μM As, the activities of SOD and GR increased by over 60% and 90%,
respectively. At 10.0 μM As, the activity of ascorbate peroxidase (APX) increased by 83%, whereas at 50.0 μM it declined significantly.
The catalase (CAT) activity, on the other hand, decreased in response to As exposure, and it corresponded to the observed
decrease in H2O2 content. We conclude that As causes a reduction in root elongation by inducing an oxidative stress that is related to enhanced
lipid peroxidation, but not to H2O2 accumulation. 相似文献
95.
96.
Navneet Dogra Julia C. Reyes Nishi Garg Punit Kohli 《Journal of visualized experiments : JoVE》2012,(66)
FRET is a process whereby energy is non-radiatively transferred from an excited donor molecule to a ground-state acceptor molecule through long-range dipole-dipole interactions1. In the present sensing assay, we utilize an interesting property of PDA: blue-shift in the UV-Vis electronic absorption spectrum of PDA (Figure 1) after an analyte interacts with receptors attached to PDA2,3,4,7. This shift in the PDA absorption spectrum provides changes in the spectral overlap (J) between PDA (acceptor) and rhodamine (donor) that leads to changes in the FRET efficiency. Thus, the interactions between analyte (ligand) and receptors are detected through FRET between donor fluorophores and PDA. In particular, we show the sensing of a model protein molecule streptavidin. We also demonstrate the covalent-binding of bovine serum albumin (BSA) to the liposome surface with FRET mechanism. These interactions between the bilayer liposomes and protein molecules can be sensed in real-time. The proposed method is a general method for sensing small chemical and large biochemical molecules. Since fluorescence is intrinsically more sensitive than colorimetry, the detection limit of the assay can be in sub-nanomolar range or lower8. Further, PDA can act as a universal acceptor in FRET, which means that multiple sensors can be developed with PDA (acceptor) functionalized with donors and different receptors attached on the surface of PDA liposomes. 相似文献
97.
We describe a program (and a website) to reformat the ClustalX/ClustalW outputs to a format that is widely used in the presentation of sequence alignment data in SNP analysis and molecular systematic studies. This program, CLOURE, CLustal OUtput REformatter, takes the multiple sequence alignment file (nucleic acid or protein) generated from Clustal as input files. The CLOURE-D format presents the Clustal alignment in a format that highlights only the different nucleotides/residues relative to the first query sequence. The program has been written in Visual Basic and will run on a Windows platform. The downloadable program, as well as a web-based server which has also been developed, can be accessed at http://imtech.res.in/~anand/cloure.html. 相似文献
98.
A model is presented of competition between sensory axons for trophic molecules (e.g. a neurotrophin such as NGF), produced in a region of skin small enough to permit their free diffusion throughout it; e.g., a touch dome, or a vibrissal follicle hair sinus. The variables specified are the number of high affinity trophic factor receptors per axon terminal and the concentration of trophic factor in the extracellular space. Previous models of this class predicted the loss of all the axons innervating the region except the one requiring least trophic factor for its maintenance, even with high rates of trophic factor production. In the present model, we have imposed upper limits to axonal growth, thereby introducing new equilibria, and we show by a global analysis using LaSalle's theorem, and also by local analysis, that several axons can then coexist if the rate of production of trophic molecules is sufficiently high. 相似文献
99.
The C-terminal thioesterase domain of the nonribosomal peptide synthetase producing the lipopetide surfactin (Srf TE) retains autonomous ability to generate the cyclic peptidolactone skeleton of surfactin when provided with a soluble beta-hydroxy-butyryl-heptapeptidyl thioester substrate. Utilizing the recently solved crystal structure [Bruner, S. D., et al. (2002) Structure 10, 301-310], the active-site nucleophile, Ser80, was changed to Cys, and the other members of the catalytic triad, Asp107 and His207, were changed to Ala, with the resulting mutants lacking detectable activity. Two cationic side chains in the active site, Lys111 and Arg120, were changed to Ala, causing an increased partitioning of the product to hydrolysis, as did a P26G mutant, mimicking the behavior of lipases. To evaluate recognition elements in substrates used by Srf TE, alterations to the fatty acyl group, the heptapeptide, and the thioester leaving group were made, and the resulting substrates were characterized for kinetic competency and flux of product to cyclization or hydrolysis. Alterations that could be accepted for cyclization were identified in all three parts of the substrate, although tolerance limits for changes varied. In addition, cocrystal structures of Srf TE with dipeptidyl boronate inhibitors were solved, illustrating the critical binding determinants of the substrate. On the basis of the structures and biochemical data, the cyclizing conformation of the surfactin peptide was modeled into the enzyme active site. 相似文献
100.
P. Vain B. Worland M. C. Clarke G. Richard M. Beavis H. Liu A. Kohli M. Leech J. Snape P. Christou H. Atkinson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(2):266-271
We have used a genotype-independent transformation system involving particle gun bombardment of immature embryos to genetically
engineer rice as part of a programme to develop resistance to nematodes. Efficient tissue culture, regeneration, DNA delivery
and selection methodologies have been established for elite African varieties (‘ITA212’, ‘IDSA6’, ‘LAC23’, ‘WAB56-104’). Twenty-five
transformed clones containing genes coding for an engineered cysteine proteinase inhibitor (oryzacystatin-IΔD86, OC-IΔD86), hygromycin resistance (aphIV) and β-glucuronidase (gusA) were recovered from the four varieties. Transformed plants were regenerated from all clones and analysed by PCR, Southern
and western blot. Detectable levels of OC-IΔD86 (up to 0.2% total soluble protein) in plant roots were measured in 12 out of 25 transformed rice lines. This level of
expression resulted in a significant 55% reduction in egg production by Meloidogyne incognita.
Received: 4 August 1997 / Accepted: 22 August 1997 相似文献