排序方式: 共有108条查询结果,搜索用时 375 毫秒
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Youngren KK Coveney D Peng X Bhattacharya C Schmidt LS Nickerson ML Lamb BT Deng JM Behringer RR Capel B Rubin EM Nadeau JH Matin A 《Nature》2005,435(7040):360-364
In mice, the Ter mutation causes primordial germ cell (PGC) loss in all genetic backgrounds. Ter is also a potent modifier of spontaneous testicular germ cell tumour (TGCT) susceptibility in the 129 family of inbred strains, and markedly increases TGCT incidence in 129-Ter/Ter males. In 129-Ter/Ter mice, some of the remaining PGCs transform into undifferentiated pluripotent embryonal carcinoma cells, and after birth differentiate into various cells and tissues that compose TGCTs. Here, we report the positional cloning of Ter, revealing a point mutation that introduces a termination codon in the mouse orthologue (Dnd1) of the zebrafish dead end (dnd) gene. PGC deficiency is corrected both with bacterial artificial chromosomes that contain Dnd1 and with a Dnd1-encoding transgene. Dnd1 is expressed in fetal gonads during the critical period when TGCTs originate. DND1 has an RNA recognition motif and is most similar to the apobec complementation factor, a component of the cytidine to uridine RNA-editing complex. These results suggest that Ter may adversely affect essential aspects of RNA biology during PGC development. DND1 is the first protein known to have an RNA recognition motif directly implicated as a heritable cause of spontaneous tumorigenesis. TGCT development in the 129-Ter mouse strain models paediatric TGCT in humans. This work will have important implications for our understanding of the genetic control of TGCT pathogenesis and PGC biology. 相似文献
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The mutational deterministic hypothesis for the origin and maintenance of sexual reproduction posits that sex enhances the ability of natural selection to purge deleterious mutations after recombination brings them together into single genomes. This explanation requires negative epistasis, a type of genetic interaction where mutations are more harmful in combination than expected from their separate effects. The conceptual appeal of the mutational deterministic hypothesis has been offset by our inability to identify the mechanistic and evolutionary bases of negative epistasis. Here we show that negative epistasis can evolve as a consequence of sexual reproduction itself. Using an artificial gene network model, we find that recombination between gene networks imposes selection for genetic robustness, and that negative epistasis evolves as a by-product of this selection. Our results suggest that sexual reproduction selects for conditions that favour its own maintenance, a case of evolution forging its own path. 相似文献
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在内径50 mm、长40 m的不锈钢水平环道内,利用压力传感器对油-气-水三相管流压力波动特性进行试验研究,从流型的观点分析三相管流平均压力梯度随液相中入口体积含水率、气相折算速度以及液相折算速度的变化规律.结果表明:油-气-水三相管流条件下的转相点对应的人口体积含水率为40%,低于油水两相管流转相点对应的体积含水率(60%),油-气-水三相流动转相的发生与折算液速、折算气速和液相含水率均有关, Lockhart&Murtinelli两相模型可以用来预测AN ‖ O/W流型的油-气-水三相流动压力梯度. 相似文献
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The insulin gene VNTR, type 2 diabetes and birth weight 总被引:12,自引:0,他引:12
Ong KK Phillips DI Fall C Poulton J Bennett ST Golding J Todd JA Dunger DB 《Nature genetics》1999,21(3):262-263
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Varon R Gooding R Steglich C Marns L Tang H Angelicheva D Yong KK Ambrugger P Reinhold A Morar B Baas F Kwa M Tournev I Guerguelcheva V Kremensky I Lochmüller H Müllner-Eidenböck A Merlini L Neumann L Bürger J Walter M Swoboda K Thomas PK von Moers A Risch N Kalaydjieva L 《Nature genetics》2003,35(2):185-189
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王海琴 《科技情报开发与经济》2005,15(14):253-255
通过对水工结构设计现状的分析,说明了水工结构计算与建筑结构计算之间的差异,指出了现在存在于水工结构设计中的,通过简单的荷载转化而利用建筑结构整体设计软件进行水工结构分析的弊端。 相似文献
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应用Pro/E Wildfire软件进行齿轮的三维设计及其齿轮机构的仿真设计,大大加深了其在教学和科研方面的实用性。 相似文献