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昆虫基因组及其大小   总被引:5,自引:0,他引:5       下载免费PDF全文
薛建  程家安  张传溪 《昆虫学报》2009,52(8):901-906
 昆虫基因组大小是由于基因组各种重复序列在扩增、缺失和分化过程中所致的数量差异造成的。这些差异使得昆虫不同类群间、种间和同种的不同种群间表现出基因组大小的不同。目前有59种昆虫已经列入基因组测序计划, 其中6种昆虫(黑腹果蝇Drosophila melanogaster、冈比亚按蚊Anopheles gambiae、家蚕Bombyx mori、意大利蜜蜂Apis mellifera、埃及伊蚊Aedes aegypti和赤拟谷盗Tribolium castaneum)的全基因组序列已经报道。有725种昆虫的基因组大小得到了估计, 大小在0.09~16.93 pg (88~16 558 Mb)之间。本文还介绍了昆虫基因组大小的估计方法, 讨论了昆虫基因组大小的变化及其意义。  相似文献
2.
piggyBac转座子及其在转基因昆虫中的应用   总被引:1,自引:0,他引:1  
piggyBac是一种从粉纹夜蛾Trichoplusiani.中分离到的、具有TTAA插入位点特异性的DNA转座子。piggyBac可在昆虫基因组中准确切离,转化频率较高,并且不受宿主因子的限制,是目前转基因昆虫研究中应用最广的转座子载体。近年来的研究发现,piggyBac类转座子广泛分布于昆虫和其他生物基因组中。文章从piggyBac的结构、转座特性、在转基因昆虫中的应用以及piggyBac类转座子的分布等几个方面综述了piggyBac的研究进展。  相似文献
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随着 DNA 测序技术的不断更新和生物信息学的快速发展,昆虫基因组学的研究与日俱增,提高了人们对种群遗传学和进化生态学的理解和认识,促进了对重要农业害虫的适应性和致害机理的研究,为安全、有效、可持续地开展害虫综合治理提供了新思路和新手段。近两年来,全球发布的昆虫基因组数量每年可达30个。在遗传学、生态学和进化论等生命科学基本原理和方法的指导下,基因组学的研究为揭示害虫遗传变异的内在机制、生态适应性策略和种群变动规律提供了重要的数据和信息资源,同时催生了一系列害虫治理新技术和新方法的研发与应用。为了进一步促进和加强基因组时代的害虫治理研究,拓展该领域研究的广度与深度,本文就昆虫基因组的研究,昆虫与植物协同进化模式及其互作机理,昆虫免疫和抗药性分子机制,以及害虫防治新技术等方面进行了综述,旨在为了解基因组时代害虫治理的研究进展及前景提供参考,对进一步改进害虫生态控制的策略和措施也具有指导意义。  相似文献
4.
叶恭银  方琦 《昆虫知识》2011,48(6):1531-1538
昆虫种类繁多,它与生态系统中的生物多样性,以及人类的日常生活和生产密切相关。自2000年黑腹果蝇Drosophila melanogaster全基因组测序完成以来,至今已先后开展了88种昆虫全基因组测序工作,这标志着昆虫学研究进入了基因组时代。本文综述了近年来昆虫基因组测序进展,以及基于基因组的昆虫学研究方法及应用等两方面的研究成果。同时,着重介绍了昆虫全基因组测序进程,昆虫基因组在个体生物学、多物种间及种群,及系统生物学研究中的应用等方面的内容。最后,还探讨了基因组时代昆虫学研究所面临的挑战。  相似文献
5.
As a subfamily of Argonaute proteins, Piwi is poorly understood compared with Ago subfamily until recent discovery of Piwi protein interacting with piRNA. We did a large scale screening of insect genomes to identify piwi-like genes. Full or partial cDNA sequences were obtained by EST elongation and GENSCAN. We found that the exon numbers were totally different between vertebrates and invertebrates, approximately 20 exons in mammals but only 6-9 exons in insects. This infers either intron insertion or loss occurred during evolution. Characterized PAZ, c-terminal PIWI domains exist in almost all predicted Piwi-like proteins. We found six conserved motifs, which contain active catalytic triad "Asp-Asp-His/Lys" required for slicer activity. The expression of siwi1 and siwi2 in Bombyx mori were verified with RT-PCR. Phylogenetic tree inferred by Bayesian algorithm indicates invertebrate Piwi-like proteins are classified into three clades, of which Ago3 clade is closer to mammalian Piwi proteins.  相似文献
6.
U7 small nuclear RNA (snRNA) sequences have been described only for a handful of animal species in the past. Here we describe a computational search for func- tional U7 snRNA genes throughout vertebrates including the upstream sequence elements characteristic for snRNAs transcribed by polymerase Ⅱ. Based on the results of this search, we discuss the high variability of U7 snRNAs in both se- quence and structure, and report on an attempt to find U7 snRNA sequences in basal deuterostomes and non-drosophilids insect genomes based on a combination of sequence, structure, and promoter features. Due to the extremely short se- quence and the high variability in both sequence and structure, no unambiguous candidates were found. These results cast doubt on putative U7 homologs in even more distant organisms that are reported in the most recent release of the Rfam database.  相似文献
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We present a detailed genome-wide comparative study of motif mismatches of microsatellites among 20 insect species representing five taxonomic orders. The results show that varying proportions (∼15–46%) of microsatellites identified in these species are imperfect in motif structure, and that they also vary in chromosomal distribution within genomes. It was observed that the genomic abundance of imperfect repeats is significantly associated with the length and number of motif mismatches of microsatellites. Furthermore, microsatellites with a higher number of mismatches tend to have lower abundance in the genome, suggesting that sequence heterogeneity of repeat motifs is a key determinant of genomic abundance of microsatellites. This relationship seems to be a general feature of microsatellites even in unrelated species such as yeast, roundworm, mouse and human. We provide a mechanistic explanation of the evolutionary link between motif heterogeneity and genomic abundance of microsatellites by examining the patterns of motif mismatches and allele sequences of single-nucleotide polymorphisms identified within microsatellite loci. Using Drosophila Reference Genetic Panel data, we further show that pattern of allelic variation modulates motif heterogeneity of microsatellites, and provide estimates of allele age of specific imperfect microsatellites found within protein-coding genes.  相似文献
8.
Active transposable elements (TEs) may result in divergent genomic insertion and abundance patterns among conspecific populations. Upon secondary contact, such divergent genetic backgrounds can theoretically give rise to classical Dobzhansky–Muller incompatibilities (DMI), thus contributing to the evolution of endogenous genetic barriers and eventually causing population divergence. We investigated differential TE abundance among conspecific populations of the nonbiting midge Chironomus riparius and evaluated their potential role in causing endogenous genetic incompatibilities between these populations. We focussed on a Chironomus‐specific TE, the minisatellite‐like Cla‐element, whose activity is associated with speciation in the genus. Using a newly generated and annotated draft genome for a genomic study with five natural C. riparius populations, we found highly population‐specific TE insertion patterns with many private insertions. A significant correlation of the pairwise FST estimated from genomewide single‐nucleotide polymorphisms (SNPs) and the FST estimated from TEs is consistent with drift as the major force driving TE population differentiation. However, the significantly higher Cla‐element FST level due to a high proportion of differentially fixed Cla‐element insertions also indicates selection against segregating (i.e. heterozygous) insertions. With reciprocal crossing experiments and fluorescent in situ hybridization of Cla‐elements to polytene chromosomes, we documented phenotypic effects on female fertility and chromosomal mispairings. We propose that the inferred negative selection on heterozygous Cla‐element insertions may cause endogenous genetic barriers and therefore acts as DMI among C. riparius populations. The intrinsic genomic turnover exerted by TEs may thus have a direct impact on population divergence that is operationally different from drift and local adaptation.  相似文献
9.
TipE is an auxiliary subunit of the Drosophila Para sodium channel. Here we describe four sequences, TEH1-4, homologous to TipE in the Drosophila melanogaster genome, harboring all typical structures of both TipE and the beta-Subunit family of big-conductance Ca(2+)-activated potassium channels: short cytosolic N- and C-terminal stretches, two transmembrane domains, and a large extracellular loop with two disulfide bonds. Whereas TEH1 and TEH2 lack the TipE-specific extension in the extracellular loop, both TEH3 and TEH4 possess two extracellular EGF-like domains. A CNS-specific expression was found for TEH1, while TEH2-4 were more widely expressed. The genes for TEH2-4 are localized close to the tipE gene on chromosome 3L. Coexpression of TEH subunits with Para in Xenopus oocytes showed a strong (30-fold, TEH1), medium (5- to 10-fold, TEH2 and TEH3), or no (TEH4) increase in sodium current amplitude, while TipE increased the current 20-fold. In addition, steady-state inactivation and the recovery from fast inactivation were altered by coexpression of Para with TEH1. We conclude that members of the TEH-family are auxiliary subunits for Para sodium channels and possibly other ion channels.  相似文献
10.
Codon usage bias refers to the phenomenon where specific codons are used more often than other synonymous codons during translation of genes, the extent of which varies within and among species. Molecular evolutionary investigations suggest that codon bias is manifested as a result of balance between mutational and translational selection of such genes and that this phenomenon is widespread across species and may contribute to genome evolution in a significant manner. With the advent of whole‐genome sequencing of numerous species, both prokaryotes and eukaryotes, genome‐wide patterns of codon bias are emerging in different organisms. Various factors such as expression level, GC content, recombination rates, RNA stability, codon position, gene length and others (including environmental stress and population size) can influence codon usage bias within and among species. Moreover, there has been a continuous quest towards developing new concepts and tools to measure the extent of codon usage bias of genes. In this review, we outline the fundamental concepts of evolution of the genetic code, discuss various factors that may influence biased usage of synonymous codons and then outline different principles and methods of measurement of codon usage bias. Finally, we discuss selected studies performed using whole‐genome sequences of different insect species to show how codon bias patterns vary within and among genomes. We conclude with generalized remarks on specific emerging aspects of codon bias studies and highlight the recent explosion of genome‐sequencing efforts on arthropods (such as twelve Drosophila species, species of ants, honeybee, Nasonia and Anopheles mosquitoes as well as the recent launch of a genome‐sequencing project involving 5000 insects and other arthropods) that may help us to understand better the evolution of codon bias and its biological significance.  相似文献
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