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121.
Ross MT Grafham DV Coffey AJ Scherer S McLay K Muzny D Platzer M Howell GR Burrows C Bird CP Frankish A Lovell FL Howe KL Ashurst JL Fulton RS Sudbrak R Wen G Jones MC Hurles ME Andrews TD Scott CE Searle S Ramser J Whittaker A Deadman R Carter NP Hunt SE Chen R Cree A Gunaratne P Havlak P Hodgson A Metzker ML Richards S Scott G Steffen D Sodergren E Wheeler DA Worley KC Ainscough R Ambrose KD Ansari-Lari MA Aradhya S Ashwell RI Babbage AK Bagguley CL Ballabio A Banerjee R Barker GE Barlow KF 《Nature》2005,434(7031):325-337
The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence. 相似文献
122.
An all-silicon Raman laser 总被引:4,自引:0,他引:4
The possibility of light generation and/or amplification in silicon has attracted a great deal of attention for silicon-based optoelectronic applications owing to the potential for forming inexpensive, monolithic integrated optical components. Because of its indirect bandgap, bulk silicon shows very inefficient band-to-band radiative electron-hole recombination. Light emission in silicon has thus focused on the use of silicon engineered materials such as nanocrystals, Si/SiO2 superlattices, erbium-doped silicon-rich oxides, surface-textured bulk silicon and Si/SiGe quantum cascade structures. Stimulated Raman scattering (SRS) has recently been demonstrated as a mechanism to generate optical gain in planar silicon waveguide structures. In fact, net optical gain in the range 2-11 dB due to SRS has been reported in centimetre-sized silicon waveguides using pulsed pumping. Recently, a lasing experiment involving silicon as the gain medium by way of SRS was reported, where the ring laser cavity was formed by an 8-m-long optical fibre. Here we report the experimental demonstration of Raman lasing in a compact, all-silicon, waveguide cavity on a single silicon chip. This demonstration represents an important step towards producing practical continuous-wave optical amplifiers and lasers that could be integrated with other optoelectronic components onto CMOS-compatible silicon chips. 相似文献
123.
Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model 总被引:111,自引:0,他引:111
The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon-climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr(-1) is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback. 相似文献
124.
Functional genomic analysis of cell division in C. elegans using RNAi of genes on chromosome III 总被引:22,自引:0,他引:22
Gönczy P Echeverri C Oegema K Coulson A Jones SJ Copley RR Duperon J Oegema J Brehm M Cassin E Hannak E Kirkham M Pichler S Flohrs K Goessen A Leidel S Alleaume AM Martin C Ozlü N Bork P Hyman AA 《Nature》2000,408(6810):331-336
Genome sequencing projects generate a wealth of information; however, the ultimate goal of such projects is to accelerate the identification of the biological function of genes. This creates a need for comprehensive studies to fill the gap between sequence and function. Here we report the results of a functional genomic screen to identify genes required for cell division in Caenorhabditis elegans. We inhibited the expression of approximately 96% of the approximately 2,300 predicted open reading frames on chromosome III using RNA-mediated interference (RNAi). By using an in vivo time-lapse differential interference contrast microscopy assay, we identified 133 genes (approximately 6%) necessary for distinct cellular processes in early embryos. Our results indicate that these genes represent most of the genes on chromosome III that are required for proper cell division in C. elegans embryos. The complete data set, including sample time-lapse recordings, has been deposited in an open access database. We found that approximately 47% of the genes associated with a differential interference contrast phenotype have clear orthologues in other eukaryotes, indicating that this screen provides putative gene functions for other species as well. 相似文献
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126.
Zusammenfassung Nachweis, dass die im Rattenharn auftretenden Metaboliten Isopropyljodid und Isopropylmethansulfonat für einen unterschiedlichen Wirkungsmechanismus der Substanzen in vivo sprechen. Aus Isopropylmethansulfonat entsteht durch einen monomolekularen Prozess das äusserst reactive Dimethylcarboniumion, während Isopropyljodid aufgrund einer bimolekularen Reaktion haupsächlich durch Hydrolyse entgiftet wird. 相似文献
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129.
Sticks used by chimpanzees in Rio Muni, West Africa 总被引:1,自引:0,他引:1
130.