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101.
Veronica J. Farmer Marija Zanic 《BioEssays : news and reviews in molecular, cellular and developmental biology》2023,45(1):2200081
Almost 40 years since the discovery of microtubule dynamic instability, the molecular mechanisms underlying microtubule dynamics remain an area of intense research interest. The “standard model” of microtubule dynamics implicates a “cap” of GTP-bound tubulin dimers at the growing microtubule end as the main determinant of microtubule stability. Loss of the GTP-cap leads to microtubule “catastrophe,” a switch-like transition from microtubule growth to shrinkage. However, recent studies, using biochemical in vitro reconstitution, cryo-EM, and computational modeling approaches, challenge the simple GTP-cap model. Instead, a new perspective on the mechanisms of microtubule dynamics is emerging. In this view, highly dynamic transitions between different structural conformations of the growing microtubule end – which may or may not be directly linked to the nucleotide content at the microtubule end – ultimately drive microtubule catastrophe. 相似文献
102.
70年代发现核小体以来,关于染色质和染色体的超微结构研究有了很大进展,对染色质的高序结构(Higher order structure)已提 相似文献
103.
Kosaku Izutsu Hidemi Sato 《Biology of the cell / under the auspices of the European Cell Biology Organization》1992,76(3):339-350
Summary— kinetochore spindle fibers in meiosis I and II grasshopper spermatocytes were cut with a heterochromatic ultraviolet (UV) microbeam converging on the specimen to form a slit-shaped microspot 1.5 × 8 μm or 3 × 8 μm. A total exposure of 3 × 10?8 joules per μm2 was administered within 0.8–2.4 s, which was sufficient for severing. The cells were observed with a high extinction polarizing microscope or phase contrast optics and a record made by time-lapse video microscopy, continuously before, during and after the irradiation. When kinetochore fibers were irradiated i anaphase with UV, an area of reduced birefringence (ARB) was produced at the exposed site. The newly created + ends of the microtubules rapidly disassembled poleward, at a constant speed of 17 μm/min. The — ends at the edge of ARB also depolymerized at a slower rate. When a kinetochore fiber was cut with UV in early anaphase at which time its associated chromosome had not disjoined from the partner chromosome, the chromosome of the irradiated kinetochore fiber moved rapidly back to its partner. The speed during this movement was faster than the normal poleward chromosome movement in anaphase by an order to magnitude or more. When a kinetochore and its associated kinetochore fiber were included in the irradiation are, the effects were more pronounced than the effects of irradiation on a kinetochore fiber alone; the direction of the line connecting the irradiated half-bivalent with the partner half-bivalent deviated so much from the longitudinal axis of the original spindle with time that the division assumed a tripolar figure. 相似文献
104.
Michael Stacey Peter Thygesen Lesley Stanley Nada Matas Angela Risch Edith Sim 《Biomarkers》1996,1(1):55-61
Arylamine N-acetyltransferase isoenzymes NAT1 and NAT2 are encoded at two polymorphic loci on human chromosome 8p22. The two loci have previously been identified using chimeric Yeast Artificial Chromosome (YAC) clones encoding either NAT1 or NAT2 as probes for metaphase chromosomes using fluorescent in situ hybridization. The 8p22 region has been demonstrated to be deleted in highly invasive bladder tumours and since NAT isoenzymes participate in the metabolism of arylamine bladder carcinogens, it is important to determine whether NAT1 and NAT2 gene loci are included in the region of deletion. We describe here the application of a cosmid clone for NAT2 as a biomarker for Fluorescent In Situ Hybridization (FISH) on interphase nuclei of exfoliated bladder cells. We also describe a 70kb probe for NAT1 which is a candidate for a suitable biomarker for use in similar FISH studies. lmmunohistochemical staining of bladder tumour sections with a polyclonal anti-peptide antibody specific for the NATl isoenzyme as a biomarker for NAT1 protein expression is also shown. 相似文献
105.
Construction and characterization of two rice bacterial artificial chromosome libraries from the parents of a permanent recombinant inbred mapping population 总被引:13,自引:0,他引:13
Hong-Bin Zhang Sangdun Choi Sung-Sick Woo Zhikang Li Rod A. Wing 《Molecular breeding : new strategies in plant improvement》1996,2(1):11-24
Rice is a leading grain crop and the staple food for over half of the world population. Rice is also an ideal species for genetic and biological studies of cereal crops and other monocotyledonous plants because of its small genome and well developed genetic system. To facilitate rice genome analysis leading to physical mapping, the identification of molecular markers closely linked to economic traits, and map-based cloning, we have constructed two rice bacterial artificial chromosome (BAC) libraries from the parents of a permanent mapping population (Lemont and Teqing) consisting of 400 F9 recombinant inbred lines (RILs). Lemont (japonica) and Teqing (indica) represent the two major genomes of cultivated rice, both are leading commercial varieties and widely used germplasm in rice breeding programs. The Lemont library contains 7296 clones with an average insert size of 150 kb, which represents 2.6 rice haploid genome equivalents. The Teqing library contains 14208 clones with an average insert size of 130 kb, which represents 4.4. rice haploid genome equivalents. Three single-copy DNA probes were used to screen the libraries and at least two overlapping BAC clones were isolated with each probe from each library, ranging from 45 to 260 kb in insert size. Hybridization of BAC clones with chloroplast DNA probes and fluorescent in situ hybridization using BAC DNA as probes demonstrated that both libraries contain very few clones of chloroplast DNA origin and are likely free of chimeric clones. These data indicate that both BAC libraries should be suitable for map-based cloning of rice genes and physical mapping of the rice genome. 相似文献
106.
107.
A simple technic is described to produce well spread gymnosperm chromosomes. Root tip meristems are digested with a pectinase:cellulase mixture to produce a cell suspension which then is squashed to yield flat, well spread chromosome complements that can be stained or used for in situ hybridization. 相似文献
108.
Klaus Werner Wolf Sabine Glatzel Frauke Niedereichholz Bryan M. Turner 《Biotechnic & histochemistry》1996,71(3):137-144
We describe a method for isolating chromosomes from testes of the desert locust, Schistocerca gregaria, and their subsequent incubation with antibodies directed against chromosomal proteins. The procedure involves hypotonic pretreatment of the germ cells, centrifugation onto coverslips in a cytocentrifuge and immunolabeling, while still unfixed, using a chromatin-stabilizing buffer. In the present case, an antibody specific for the acetylated isoforms of his tone H4 was tested. After the antibody treatment, the preparations are fixed using formaldehyde, stained with a DNA-specific fluorescent dye and mounted. Analysis of the preparations revealed good preservation of chromosome structure in prophase spermatogonia and late prophase I spermatocytes. Fully condensed chromosomes were not observed and are probably lost during preparation. The bright fluorescence of the autosomes indicates that the reaction between the antibody against acetylated histone H4 and its chromosomal antigen is not impeded. In contrast, the X univalent remained unstained with the exception of a small terminal band. Thus, cytospin preparations of locust germ cells allow high resolution immunolabeling with antibodies against chromosome-associated proteins. 相似文献
109.
110.
A 19-kb CpG Island Associated with Single-minded Gene 2 in Down Syndrome Chromosomal Region 总被引:1,自引:0,他引:1
Osoegawa Kazutoyo; Okano Saishi; Kato Yasutake; Nishimura Yukinobu; Soeda Eiichi 《DNA research》1996,3(3):175-179
To help in isolating the genes involved in Down syndrome, wesought CpG islands in 4 Mb cosmid/PAC contigs spanning mostof the 21q.22.2 band using seven rare cutting enzymes. A strikingfeature was observed upstream of hSIM2 where at least 41 rare-cuttingsites were clustered within a 20-kb region. To investigate thestructure of the cluster, a cosmid containing hSIM2 was submittedto shotgun sequencing. Sequence analysis revealed that the clusterwas a long CpG island extending 19, 128 nucleotides which includesin the first and second exons of hSIM2. Taken together withour observation in which the CpG islands were concentrated within1.2 Mb around hSIM2, we propose that this region functions asan R-band, and the cluster provides a unique element for markingof DNA for the spatial and temporal expression of the hSIM2locus. 相似文献