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排序方式: 共有873条查询结果,搜索用时 15 毫秒
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Maria Råstam Christopher Gillberg Jan Wahlström† 《Journal of child psychology and psychiatry, and allied disciplines》1991,32(4):695-701
Forty-seven cases with anorexia nervosa (including a total population group) and 47 sex-, age-, and school-matched comparison cases were subjected to chromosome analyses in a blind fashion. No major abnormalities were found in any of the cases. Sex chromatin was analysed in buccal smears from the girls. No differences between the anorexia nervosa and the comparison cases were found. It seems that chromosomal/sex chromatin analyses in anorexia nervosa are not warranted. 相似文献
4.
D. H. Jacobs 《Chromosome research》2004,12(2):175-191
Sibling subspecies of Dundocoris nodulicarinus, inhabiting different isolated indigenous evergreen forests in South Africa, have chromosome numbers of 2n(male) = 14XY, 9XY1Y2 and 7XY1Y2. The ancestral chromosome number of Dundocoris is probably 2n(male) = 28XY and several chromosome fusions were involved in the karyotype evolution of these taxa. The XY1Y2 sex chromosome system of the 9XY1Y2 D. nodulicarinus novenus originated by the fusion of a large autosome with the X-chromosome, forming a neo-X with the homologue of the fused autosome forming the neo-Y (=Y1) and the original Y-chromosome, the Y2. While the original X- and Y-chromosomes are heterochromatic and heteropycnotic during prophase I, the autosomal part of the neo-X and the neo-Y stay euchromatic and behave like a normal autosomal pair, forming synapsis and chiasmata. The XY1Y2 sex chromosome system of the 7XY1Y2 D. nodulicarinus septeni probably originated from the 9XY1Y2 karyotype when the homologous chromosomes of a small autosomal pair fused with the original X- and Y-chromosomes, respectively. In both the subspecies with the neo-XY1Y2 systems, the original sex chromosomes still undergo chromatid segregation at anaphase I (= post-reductional). The evolution and behaviour of the karyotypes and sex chromosome systems during the course of meiosis in the subspecies of D. nodulicarinus are described, discussed and illustrated. 相似文献
5.
Ljudmila Solovjeva Maria Svetlova Grigory Stein Vadim Chagin Yuryi Rozanov Maria Zannis-Hadjopoulos Gerald Price Nikolai Tomilin 《Chromosome research》1998,6(8):595-602
Recent statistical analysis of the folding of G0/G1 chromosomes using fluorescence in situ hybridization (FISH) allowed development of a random walk/giant loop model of chromosome structure. According to this model there are two levels of organization of G0/G1 chromosome fibres. On the first level, the fibres are arranged in giant loops several Mbp in size, and within each loop the fibres are randomly folded. On the second level, the loop attachment sites form a chromosome backbone that also shows random folding. Newly replicated segments of mammalian chromosomes may be directly visualized at high resolution in S-phase nuclei using immunofluorescent methods and appear as worm-like fibres. In our earlier study, we analysed conformation of the fibres in human cells blocked for 16 h at the G1/S boundary with 5- fluorodeoxyuridine (FdU) and then released into S-phase by the addition of a DNA prec ursor. However, long treatment of cells with FdU induces very short replicons and may promote apoptosis. In this study we analysed conformation of the fibres in normally proliferating human cells that had not been blocked with FdU for a long time. It has been found that replicated chromosome fibres visualized just after 2 h of incubation of the cells with a non-radioactively labelled DNA precursor behave as flexible polymer chains without major constraints, and that their local conformation in the range of several microns of their contour length may be considered as random. Confocal analysis of human X chromosomes visualized in HeLa cells using FISH with a specific painting probe shows that in S-phase the chromosomes occupy distinct nuclear territories and their apparent size does not differ from that in non-S-phase cells. This observation indicates that the second level of chromosome organization also exists in S-phase chromosomes. It appears, theref ore, that the random walk/giant loop model developed earlier for G0/G1 chromosomes is also valid for S-phase chromosomes. 相似文献
6.
Over the past 100 years Drosophila has been developed into an outstanding model system for the study of evolutionary processes. A fascinating aspect of evolution
is the differentiation of sex chromosomes. Organisms with highly differentiated sex chromosomes, such as the mammalian X and
Y, must compensate for the imbalance in gene dosage that this creates. The need to adjust the expression of sex-linked genes
is a potent force driving the rise of regulatory mechanisms that act on an entire chromosome. This review will contrast the
process of dosage compensation in Drosophila with the divergent strategies adopted by other model organisms. While the machinery of sex chromosome compensation is different
in each instance, all share the ability to direct chromatin modifications to an entire chromosome. This review will also explore
the idea that chromosome-targeting systems are sometimes adapted for other purposes. This appears the likely source of a chromosome-wide
targeting system displayed by the Drosophila fourth chromosome. 相似文献
7.
Summary Cell cultures (GTS) of epithelioid nature derived from the skin of a green sea turtle,Chelonia mydas, were treated with colchicine at a final concentration of 0.5 g/ml for 16 h. Mitotic cells were harvested by brief treatment with trypsin-Versene, subjected to hypotonic solution (1% sodium citrate) and fixed in (13) acetic acid: methanol. Giemsa stained preparations were photographed on High Contrast Copy film under phase contrast optics using a bluegreen filter. The result was significant enhancement of the microchromosome portion of the complement morphologically characteristic of reptilian metaphase chromosomes. By this method it was determined that the GTS cell line retains the female diploid number of the Chelonia species. 相似文献
8.
Telomeres, besides their main role in the protection and maintenance of chromosome ends, have several other vital functions
in the cell cycle. We studied their role in the achiasmatic meiosis of female Lepidoptera, insects with holokinetic chromosomes.
By fluorescence in-situ hybridization (FISH) with the insect telomeric probe, (TTAGG)
n
, we mapped the distribution of telomeric and interstitial telomeric sequences (ITS) in female meiotic chromosomes of two
species, Orgyia antiqua with a reduced chromosome number (2n=28) and Ephestia kuehniella mutants, possessing a radiation-induced chromosome fusion in the genome (2n=59). In addition to the strong typical telomeric signals, O. antiqua displayed weaker hybridization signals in interstitial sites of pachytene bivalents. The observed ITS most probably reflect
remnants of chromosomal rearrangements and support the hypothesis that the Orgyia karyotype had arisen by multiple fusions of ancestral chromosomes. On the other hand, the absence of ITS in the chromosome
fusion of Ephestia indicated the loss of telomeres before the two original chromosomes fused. When the telomeric probe was amplified by enzymatic
reaction with tyramid, the number of ITS observed increased in Orgyia, and a few ITS were also observed in several chromosomes of Ephestia but not in the fused chromosome. This suggests that the genomes of both species also contain ITS other than those originating
from chromosome fusions. The analysis of female meiotic prophase I revealed non-homologous associations of postpachytene bivalents
mediated by telomeric DNA, which were not observed in the pachytene stage. Surprisingly, in early postpachytene nuclei the
telomeric associations also involved ITS, whereas later postpachytene nuclei displayed chains of bivalents interconnected
only by true telomeres. This finding favours a hypothesis that telomeric associations between bivalents play a role in chromosome
segregation in the achiasmatic meiosis of female Lepidoptera.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Claudio Oliveira Fausto Foresti Marcos Guilherme Rigolino Yara Aiko Tabata 《Chromosome research》1995,3(3):182-190
The surface-spreading synaptonemal complex (SC) technique was employed to analyze spermatocytes and oocytes of rainbow trout in order to visualize the process of autosome and sex chromosome synapsis in this species. The structure of lateral elements (LEs) of the SC and the chromosome synapsis process at the stages of leptotene, zygotene and pachytene are described. Comparative analysis of SCs of spermatocytes and oocytes showed a difference in the synaptic process, i.e. in spermatocytes all LEs were synapsed before the appearance of centromeric regions in the biarmed elements, while in the oocytes some fully synapsed LEs, including the centromeric region of the biarmed elements, were found together with fully or partially unsynapsed LEs. In males the sex chromosome synapsis starts only after all autosomes have synapsed. Irregular synapses involving three or four LEs were found in 3.4% of the cells analyzed in mid or late zygotene. Multivalents were found in males and females. Some aspects of initial meiotic development and their implications in rainbow trout cytogenetics, genetics and evolution are discussed. 相似文献
10.
Beverly J. White Clare Crandall Jaap Goudsmit Chuck H. Morrow David W. Alling D. Carleton Gajdusek J -H. Tijio John M. Opitz 《American journal of medical genetics. Part A》1981,10(1):77-89
We present cytogenetic findings in 7 familial and 5 sporadic Alzheimer disease (AD) patients and 34 unaffected relatives, spouses, and normal controls. Our study was prompted by reports of increased chromosome abnormalities in patients and family members at risk for AD. Coded peripheral blood chromosome preparations were evaluated for aneuploidy, aberration rates, and banding patterns. Statistical analyses of our results showed no increase in aneuploidy or aberrations in AD patients, their relatives, or normals. Chromosome loss or gain in aneuploid cells was not specific except in two individuals. These two older persons studied, one with AD and one unaffected, were observed to have increased sex chromosome aneuploidy. This finding was attributed to aging and was not considered to be an effect of AD. 相似文献