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111.
Evolution of genes and genomes on the Drosophila phylogeny 总被引:2,自引:0,他引:2
Drosophila Genomes Consortium Clark AG Eisen MB Smith DR Bergman CM Oliver B Markow TA Kaufman TC Kellis M Gelbart W Iyer VN Pollard DA Sackton TB Larracuente AM Singh ND Abad JP Abt DN Adryan B Aguade M Akashi H Anderson WW Aquadro CF Ardell DH Arguello R Artieri CG Barbash DA Barker D Barsanti P Batterham P Batzoglou S Begun D Bhutkar A Blanco E Bosak SA Bradley RK Brand AD Brent MR Brooks AN Brown RH Butlin RK Caggese C Calvi BR Bernardo de Carvalho A Caspi A Castrezana S Celniker SE 《Nature》2007,450(7167):203-218
Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species. 相似文献
112.
Solid-state cavity quantum electrodynamics (QED) systems offer a robust and scalable platform for quantum optics experiments and the development of quantum information processing devices. In particular, systems based on photonic crystal nanocavities and semiconductor quantum dots have seen rapid progress. Recent experiments have allowed the observation of weak and strong coupling regimes of interaction between the photonic crystal cavity and a single quantum dot in photoluminescence. In the weak coupling regime, the quantum dot radiative lifetime is modified; in the strong coupling regime, the coupled quantum dot also modifies the cavity spectrum. Several proposals for scalable quantum information networks and quantum computation rely on direct probing of the cavity-quantum dot coupling, by means of resonant light scattering from strongly or weakly coupled quantum dots. Such experiments have recently been performed in atomic systems and superconducting circuit QED systems, but not in solid-state quantum dot-cavity QED systems. Here we present experimental evidence that this interaction can be probed in solid-state systems, and show that, as expected from theory, the quantum dot strongly modifies the cavity transmission and reflection spectra. We show that when the quantum dot is coupled to the cavity, photons that are resonant with its transition are prohibited from entering the cavity. We observe this effect as the quantum dot is tuned through the cavity and the coupling strength between them changes. At high intensity of the probe beam, we observe rapid saturation of the transmission dip. These measurements provide both a method for probing the cavity-quantum dot system and a step towards the realization of quantum devices based on coherent light scattering and large optical nonlinearities from quantum dots in photonic crystal cavities. 相似文献
113.
有目的的选择是任何一家企业都必须要面临的决策之一。而最成功的公司都会非常清醒地去选择它们将要提供的产品、服务、客户群和营销渠道。与选择并驾齐驱的、摆在企业面前的另一重大挑战是:如何更好的利用有限资源——时间、金钱和人力资源——进行投资。所以,在销售、营销和服务的数据库中进行有目的的划分以提高有意识的选择将成为公司客户管理活动最有价值的奖品。并非所有的顾客都是平等的,因此,必须将有限的资源投入到那些最有潜在价值顾客身上,也就是将有限的资源直接投入到最能够得到回报的地方。我将这一举措称之为“以顾客需要为… 相似文献
114.
115.
CpG island methylator phenotype underlies sporadic microsatellite instability and is tightly associated with BRAF mutation in colorectal cancer 总被引:19,自引:0,他引:19
Weisenberger DJ Siegmund KD Campan M Young J Long TI Faasse MA Kang GH Widschwendter M Weener D Buchanan D Koh H Simms L Barker M Leggett B Levine J Kim M French AJ Thibodeau SN Jass J Haile R Laird PW 《Nature genetics》2006,38(7):787-793
Aberrant DNA methylation of CpG islands has been widely observed in human colorectal tumors and is associated with gene silencing when it occurs in promoter areas. A subset of colorectal tumors has an exceptionally high frequency of methylation of some CpG islands, leading to the suggestion of a distinct trait referred to as 'CpG island methylator phenotype', or 'CIMP'. However, the existence of CIMP has been challenged. To resolve this continuing controversy, we conducted a systematic, stepwise screen of 195 CpG island methylation markers using MethyLight technology, involving 295 primary human colorectal tumors and 16,785 separate quantitative analyses. We found that CIMP-positive (CIMP+) tumors convincingly represent a distinct subset, encompassing almost all cases of tumors with BRAF mutation (odds ratio = 203). Sporadic cases of mismatch repair deficiency occur almost exclusively as a consequence of CIMP-associated methylation of MLH1 . We propose a robust new marker panel to classify CIMP+ tumors. 相似文献
116.
Lgr5 marks cycling, yet long-lived, hair follicle stem cells 总被引:1,自引:0,他引:1
Jaks V Barker N Kasper M van Es JH Snippert HJ Clevers H Toftgård R 《Nature genetics》2008,40(11):1291-1299
In mouse hair follicles, a group of quiescent cells in the bulge is believed to have stem cell activity. Lgr5, a marker of intestinal stem cells, is expressed in actively cycling cells in the bulge and secondary germ of telogen hair follicles and in the lower outer root sheath of anagen hair follicles. Here we show that Lgr5(+) cells comprise an actively proliferating and multipotent stem cell population able to give rise to new hair follicles and maintain all cell lineages of the hair follicle over long periods of time. Lgr5(+) progeny repopulate other stem cell compartments in the hair follicle, supporting the existence of a stem or progenitor cell hierarchy. By marking Lgr5(+) cells during trafficking through the lower outer root sheath, we show that these cells retain stem cell properties and contribute to hair follicle growth during the next anagen. Expression analysis suggests involvement of autocrine Hedgehog signaling in maintaining the Lgr5(+) stem cell population. 相似文献
117.
Sexual conflict reduces offspring fitness in zebra finches 总被引:5,自引:0,他引:5
Parental care is often costly; hence, in sexually reproducing species where both male and female parents rear their offspring (biparental care), sexual conflict over parental investment can arise. Such conflict occurs because each care-giver would benefit from withholding parental investment for use with another partner, leading to a reduction in the amount of care given by one parent at the expense of the other. Here we report experiments to explore the prediction from theory that parents rearing offspring alone may provide greater parental investment than when rearing offspring together with a partner. We found that when the number of offspring per parent, and hence the potential workload, were kept constant, offspring received a greater per capita parental investment from single females than from both parents working together, and that males reared by single mothers were more sexually attractive as adults than their biparentally reared siblings. This difference between single- and two-parent families is due to a reduction in care provided by females when they care together with a male, rather than laziness by males or differences in the begging behaviour of chicks, supporting the claim that sexual conflict in biparental care can reduce the quality of offspring raised. 相似文献
118.
Hinch AG Tandon A Patterson N Song Y Rohland N Palmer CD Chen GK Wang K Buxbaum SG Akylbekova EL Aldrich MC Ambrosone CB Amos C Bandera EV Berndt SI Bernstein L Blot WJ Bock CH Boerwinkle E Cai Q Caporaso N Casey G Cupples LA Deming SL Diver WR Divers J Fornage M Gillanders EM Glessner J Harris CC Hu JJ Ingles SA Isaacs W John EM Kao WH Keating B Kittles RA Kolonel LN Larkin E Le Marchand L McNeill LH Millikan RC Murphy A Musani S Neslund-Dudas C Nyante S Papanicolaou GJ Press MF Psaty BM 《Nature》2011,476(7359):170-175
Recombination, together with mutation, gives rise to genetic variation in populations. Here we leverage the recent mixture of people of African and European ancestry in the Americas to build a genetic map measuring the probability of crossing over at each position in the genome, based on about 2.1 million crossovers in 30,000 unrelated African Americans. At intervals of more than three megabases it is nearly identical to a map built in Europeans. At finer scales it differs significantly, and we identify about 2,500 recombination hotspots that are active in people of West African ancestry but nearly inactive in Europeans. The probability of a crossover at these hotspots is almost fully controlled by the alleles an individual carries at PRDM9 (P?value 10(-245)). We identify a 17-base-pair DNA sequence motif that is enriched in these hotspots, and is an excellent match to the predicted binding target of PRDM9 alleles common in West Africans and rare in Europeans. Sites of this motif are predicted to be risk loci for disease-causing genomic rearrangements in individuals carrying these alleles. More generally, this map provides a resource for research in human genetic variation and evolution. 相似文献
119.
Peter Barker 《Studies in history and philosophy of science》1980,11(3):243-256
120.