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排序方式: 共有221条查询结果,搜索用时 15 毫秒
211.
Herwin Eding Richard PMA Crooijmans Martien AM Groenen Theo HE Meuwissen 《遗传、选种与进化》2002,34(5):613-633
The quantitative assessment of genetic diversity within and between populations is important for decision making in genetic conservation plans. In this paper we define the genetic diversity of a set of populations, S, as the maximum genetic variance that can be obtained in a random mating population that is bred from the set of populations S. First we calculated the relative contribution of populations to a core set of populations in which the overlap of genetic diversity was minimised. This implies that the mean kinship in the core set should be minimal. The above definition of diversity differs from Weitzman diversity in that it attempts to conserve the founder population (and thus minimises the loss of alleles), whereas Weitzman diversity favours the conservation of many inbred lines. The former is preferred in species where inbred lines suffer from inbreeding depression. The application of the method is illustrated by an example involving 45 Dutch poultry breeds. The calculations used were easy to implement and not computer intensive. The method gave a ranking of breeds according to their contributions to genetic diversity. Losses in genetic diversity ranged from 2.1% to 4.5% for different subsets relative to the entire set of breeds, while the loss of founder genome equivalents ranged from 22.9% to 39.3%. 相似文献
212.
BLM and SLX4 play opposing roles in recombination‐dependent replication at human telomeres
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Alexander P Sobinoff Joshua AM Allen Axel A Neumann Sile F Yang Monica E Walsh Jeremy D Henson Roger R Reddel Hilda A Pickett 《The EMBO journal》2017,36(19):2907-2919
Alternative lengthening of telomeres (ALT) is a telomere lengthening pathway that predominates in aggressive tumors of mesenchymal origin; however, the underlying mechanism of telomere synthesis is not fully understood. Here, we show that the BLM–TOP3A–RMI (BTR) dissolvase complex is required for ALT‐mediated telomere synthesis. We propose that recombination intermediates formed during strand invasion are processed by the BTR complex, initiating rapid and extensive POLD3‐dependent telomere synthesis followed by dissolution, with no overall exchange of telomeric DNA. This process is counteracted by the SLX4–SLX1–ERCC4 complex, which promotes resolution of the recombination intermediate, resulting in telomere exchange in the absence of telomere extension. Our data are consistent with ALT being a conservative DNA replication process, analogous to break‐induced replication, which is dependent on BTR and counteracted by SLX4 complex‐mediated resolution events. 相似文献
213.
Petra Mlcochova Katherine A Sutherland Sarah A Watters Cosetta Bertoli Rob AM de Bruin Jan Rehwinkel Stuart J Neil Gina M Lenzi Baek Kim Asim Khwaja Matthew C Gage Christiana Georgiou Alexandra Chittka Simon Yona Mahdad Noursadeghi Greg J Towers Ravindra K Gupta 《The EMBO journal》2017,36(5):604-616
An unresolved question is how HIV‐1 achieves efficient replication in terminally differentiated macrophages despite the restriction factor SAMHD1. We reveal inducible changes in expression of cell cycle‐associated proteins including MCM2 and cyclins A, E, D1/D3 in macrophages, without evidence for DNA synthesis or mitosis. These changes are induced by activation of the Raf/MEK/ERK kinase cascade, culminating in upregulation of CDK1 with subsequent SAMHD1 T592 phosphorylation and deactivation of its antiviral activity. HIV infection is limited to these G1‐like phase macrophages at the single‐cell level. Depletion of SAMHD1 in macrophages decouples the association between infection and expression of cell cycle‐associated proteins, with terminally differentiated macrophages becoming highly susceptible to HIV‐1. We observe both embryo‐derived and monocyte‐derived tissue‐resident macrophages in a G1‐like phase at frequencies approaching 20%, suggesting how macrophages sustain HIV‐1 replication in vivo. Finally, we reveal a SAMHD1‐dependent antiretroviral activity of histone deacetylase inhibitors acting via p53 activation. These data provide a basis for host‐directed therapeutic approaches aimed at limiting HIV‐1 burden in macrophages that may contribute to curative interventions. 相似文献
214.
Visualization of cytosolic ribosomes on the surface of mitochondria by electron cryo‐tomography
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We employed electron cryo‐tomography to visualize cytosolic ribosomes on the surface of mitochondria. Translation‐arrested ribosomes reveal the clustered organization of the TOM complex, corroborating earlier reports of localized translation. Ribosomes are shown to interact specifically with the TOM complex, and nascent chain binding is crucial for ribosome recruitment and stabilization. Ribosomes are bound to the membrane in discrete clusters, often in the vicinity of the crista junctions. This interaction highlights how protein synthesis may be coupled with transport. Our work provides unique insights into the spatial organization of cytosolic ribosomes on mitochondria. 相似文献
215.
The anti-algal activity of five macrophyte extracts on the cyanobacterium Microcystis aeruginosa in Egypt was investigated in 2013. Extract activity varied according to plant type, extracting solvent and its concentration. The highest inhibitory activity was achieved with ethanol extract at a concentration of 80 mg l?1, followed by chloroformic extracts, at 60 mg l?1. Methanolic extracts of Eichhornia crassipes and Polygonum tomentosum inhibited growth of Microcystis aeruginosa at all concentrations. Acetonic extracts inhibited algal growth at 60 mg l?1, except for the extract of Ceratophyllum subdemersum, which showed stimulation of M. aeruginosa growth. Eichhornia crassipes ethanolic extract exerted the most powerful inhibition by more than five-fold, 570.17%, followed by those of P. tomentosum, Saccharum spontaneum, Ceratophyllum demersum and C. subdemersum, 559.48, 553.99, 544.11 and 366.51%, respectively. Phytochemical screening for the tested plant extracts revealed the presence of biologically active substances of different concentrations, with P. tomentosum having the highest polyphenols, 1.95% of dry weight. 相似文献
216.
217.
K van Oers A W Santure I De Cauwer N EM van Bers R PMA Crooijmans B C Sheldon M E Visser J Slate M AM Groenen 《Heredity》2014,112(3):307-316
Linking variation in quantitative traits to variation in the genome is an important, but
challenging task in the study of life-history evolution. Linkage maps provide a valuable
tool for the unravelling of such trait−gene associations. Moreover, they give
insight into recombination landscapes and between-species karyotype evolution. Here we
used genotype data, generated from a 10k single-nucleotide polymorphism (SNP) chip, of
over 2000 individuals to produce high-density linkage maps of the great tit (Parus
major), a passerine bird that serves as a model species for ecological and
evolutionary questions. We created independent maps from two distinct populations: a
captive F2-cross from The Netherlands (NL) and a wild population from the United Kingdom
(UK). The two maps contained 6554 SNPs in 32 linkage groups, spanning 2010 cM and
1917 cM for the NL and UK populations, respectively, and were similar in size and
marker order. Subtle levels of heterochiasmy within and between chromosomes were
remarkably consistent between the populations, suggesting that the local departures from
sex-equal recombination rates have evolved. This key and surprising result would have been
impossible to detect if only one population was mapped. A comparison with zebra finch
Taeniopygia guttata, chicken Gallus gallus and the green anole lizard
Anolis carolinensis genomes provided further insight into the evolution of
avian karyotypes. 相似文献
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