环境对果蝇P转座因子的作用关系研究

转座因子,重组、整合、遗传效应等是目前遗传学领域的一个研究热题。转座因子对遗传变异、宗系进化、突变频率、物种形成、新基因的产生以及对分子生物学、遗传工程学、群体遗传学和数量遗传学等方面的研究都有着重要的意义,主要对果蝇的P转座因子以及环境对P转座因子遗传效应的作用关系进行了研究。     

转座因子和宿主基因组的进化

转座因子主要是一些“自在”或“无功能”的DNA,其对宿主进化无关紧要的观点受到了质疑。新近的报道指出,它们有增强宿主基因组自身进化,对环境变化作出反应的潜在能力,很可能是遗传多样性的主要源泉。     

果蝇P转座因子的研究进展

果蝇P因子是DNA转座子,在近几十年里受到很大关注。可用于确认有关基因,克隆基因以及安置基因回到基因组。P因子的高易动性及其保持和对内部序列强烈的修饰作用也是P因子的本质特征。P因子的另一重要用途是用于产生转基因果蝇。目的基因置于质粒内P因子中可在转座酶的作用下插入前胚盘胚。携带目的基因的P因子可从质粒转座到任意染色体上。据报道,在典型实验中,插入可育果蝇的10％～20％可产生转化体后裔。但是以这种可动DNA片段作为载体尚存在转移基因的不稳定性及与内源跳跃基因的相互影响。本文介绍了果蝇P转座因子的一些研究进展。这些因子的遗传可动性也使它们适用于建造载体产生转基因生物。若如此,载体导入外源基因组的遗传稳定性问题将是一个重要课题。 Abstract：P elements in D.melanogaster are DNA transposons and received greater attention within the last few decades.P elements are used for identifying genes of interest,for cloning them,and for placing them back into the genome.The high mobility of P elements and their retention of this mobility and drastic modiffications to their internal sequences are also essential features.Another most important use of P elements is that of making transgenic flies.Desired gene is placed between P-element ends,usually within a plasmid,and injected into preblastoderm embryos in the presence of transposase.This P element then transposes from the plasmid to a random chromosomal site.Reported in a typical experiment,10％～20％ of the fertile injected flies produce transformant progeny.But the instability of the transferred gene carried on a piece of mobile DNA as a vector and its interaction with endogenous jumping genes.This paper introduced the studies advances of P transposable element in Drosophila.The genetic mobility of these elements can also make them suitable for the construction of vectors to create transgenic organisms.If so,the genetic stability of the vectors introduced to a foreign genome should be a important subject.     

谈谈转座因子

传统的基因概念认为基因在染色体上是一个稳定的实体,它是不会改变其功能的,除非发生基因突变。而且基因不会任意移动位置和插入到其它染色体中去。但是近年的研究表明,有些遗传因子或基因不仅能改变功能,而且可以任意移动而改变原来的位置。这种可移动的基因或核苷酸顺序被切下后可整合到其它染色体上,这种移动现象称转座。这种可转移位置的因子称转座因子(transposable ele-ments)也称跳跃基因(jumping gene)。早在1932年,麦克林托克(Mc Clintock)     

植物转座因子

转座因子 (ｔｒａｎｓｐｏｓａｂｌｅｅｌｅｍｅｎｔ ,ＴＥｓ)是指在生物细胞中能从同一条染色体的一个位点转移到另一个位点或者从一条染色体转移到另一条染色体上的ＤＮＡ序列。 1 947年美国冷泉港实验室的“玉米夫人”ＭｃＣｌｉｎｔｏｃｋ首先在玉米中发现并描述了转座因子。转座因子的发现 ,打破了传统遗传学上关于基因在染色体上固定排列及同源染色体交换的观念 ,揭示了基因的流动性 ,具有重要的意义。1 .转座因子的结构特点和分类到目前报道为止 ,至少在 32种植物上有转座因子存在 ,其中研究最多的是玉米、金鱼草、拟南芥等[1] 。其…     

谈谈改变传统观念的转座因子

在五十年代前,人们一直认为每一基因组的 DNA是固定的,包括位置固定、数目固定。转座因子的发现修正了这一观念。现在人们认识到基因组中的某些成分的位置常常是不固定的,一种生物的基因组大小或基因的数目也并非绝对不变。这种位置不固定的成分乃是转座因子。转座因子(transpos-able element)是细胞中能够改变自身位置的一段 DNA 序列。转座因子改变位置的行为称转座(transposition),转座可以发生在同一染色体的不同位置之间,不同的     

转座因子在肺炎链球菌耐药进化中的作用

要肺炎链球菌的耐药决定子由染色体上的转座因子携带,与耐药相关的转座因子和转移的主要方式有：①接合转座子：携带erm(B)、tet(M)和aphA-3等的Tn916-Tn1545家族,通过接合转移;②缺陷转座子：携带mef基因及ABC外排系统的Tn1207．1和mega插入元件,可转化到敏感菌株引起耐药;③复合转座子：由mega插入元件与Tn916整合产生的Tn2009,以转化方式转移。肺炎链球菌通过转座因子获得并传播耐药基因,在其耐药进化中起重要作用。     

哺乳动物PB转座因子研究

人类基因组计划发现哺乳动物体内存在大约30000个基因,将遗传蓝图的“天书”展示在人们面前。我国科研人员为此贡献了1％的测序结果。目前,国际竞争的焦点已经转向如何迅速了解这些基因的功能,从中找出有重大理论意义及经济效益的基因,即功能基因组研究。哺乳动物基因功能研究不仅有助于人类认识自我,具有重要的理论意义,而且疾病相关基因的研究也对发展针对性的预防、诊断和治疗手段具有决定性作用,因而成为世界生物科技产业竞争的焦点。     

可转座基因与植物基因组多样性

高等植物基因组含有大量各式各样的串联重复序列和出现频率很高的散布重复序列,如转座子、反转座子、短散布核元件和一些新发现的小型转座子等,它们当中的大多数是具有移动能力的可转座基因.这些可转座基因在漫长的进化过程中对基因和基因组多样性的形成所起的作用,成为近年来分子生物学领域中的重要研究内容.     

杆状病毒转座因子研究进展

转座因子(Transposable elements)是一类可移动转座的遗传因子的统称,包括原核生物中的插入(IS)、转座子(Tn)、质粒;真核生物中的Ty,P因子,2μDNA,Copia因子,以及噬菌体Mu和反转录病毒等。因此,转座因子又称可移动的遗传因子(Mobile genetic element)。转座因子最早由美国科学家Barbara McClintock于1956年在玉米染色体中发现,并于1984年被授予诺贝尔医学或生理学奖。转座因子的发现无论在理论上还是实践上都具有很重要的意义,被认为是遗传学发展史上的重要里程碑之一。杆状病毒是一类以节肢动物(主要发现于昆虫纲鳞翅目)为宿主的病毒的统称。杆状病毒亦存在转座因子。对杆状病毒转座因子的研究起源于对感     

Accumulation of Transposable Elements in the Heterochromatin and on the Y Chromosome of Drosophila simulans and Drosophila melanogaster

The elements of the transposon families G, copia, mdg 1, 412, and gypsy that are located in the heterochromatin and on the Y chromosome have been identified by the Southern blotting technique in Drosophila simulans and D. melanogaster populations. Within species, the abundance of such elements differs between transposon families. Between species, the abundance in the heterochromatin and on the Y chromosome of the elements of the same family can differ greatly suggesting that differences within a species are unrelated to structural features of elements. By shedding some new light on the mechanism of accumulation of transposable elements in the heterochromatin, these data appear relevant to the understanding of the long-term interaction between transposable elements and the host genome. Received: 8 August 1997 / Accepted: 11 December 1997     

Molecular Evolution of P Transposable Elements in the Genus Drosophila. II. The obscura Species Group

A phylogenetic analysis of P transposable elements in the Drosophila obscura species group is described. Multiple P sequences from each of 10 species were obtained using PCR primers that flank a conserved region of exon 2 of the transposase gene. In general, the P element phylogeny is congruent with the species phylogeny, indicating that the dominant mode of transmission has been vertical, from generation to generation. One manifestation of this is the distinction of P elements from the Old World obscura and subobscura subgroups from those of the New World affinis subgroup. However, the overall distribution of elements within the obscura species group is not congruent with the phylogenetic relationships of the species themselves. There are at least four distinct subfamilies of P elements, which differ in sequence from each other by as much as 34%, and some individual species carry sequences belonging to different subfamilies. P sequences from D. bifasciata are particularly interesting. These sequences belong to two subfamilies and both are distinct from all other P elements identified in this survey. Several mechanisms are postulated to be involved in determining phylogenetic relationships among P elements in the obscura group. In addition to vertical transmission, these include retention of ancestral polymorphisms and horizontal transfer by an unknown mating-independent mechanism.     

Drosophila melanogaster P Transposable Elements: Mechanisms of Transposition and Regulation

The molecular mechanisms that control P element transposition and determine its tissue specificity remain incompletely understood, although much information has been compiled about this element in the last decade. This review summarizes the currently available information about P element transposition, P-M hybrid dysgenesis and P cytotype features, P element-encoded repressors, and regulation of transposition.     

Transposable elements and the penetrance of quantitative characters in Drosophila melanogaster

We wanted to determine whether there is a correlation between the quantitative character, the penetrance of the loss of humeral bristles in scute lines, and the distribution of transposable genetic elements in their genomes. We derived 18 isogenic lines with penetrance ranging between 2.8% and 92.0% from six mutant lines. The localization of the transposable elements (TEs) P, mdg1, Dm412, copia, gypsy and B104 was determined in all isogenic derivatives by in situ hybridization. The total number of the TE sites over all lines was 180. A comparison of the distribution of the TEs in the isogenic lines revealed the location of sites typical of lines with similar penetrance, no matter which parental line was involved. The results obtained suggest that such typical sites appear to tag the genome regions where the polygenes affecting the character in question are most likely to be found.     

植物基因组中微型反向重复转座元件研究进展

微型反向重复转座元件(miniature inverted repeat transposable element,MITE)是一类特殊的转座元件,在结构上与有缺失的DNA转座子相似,但具有反转录转座子高拷贝数的特点.MITE时常与基因相伴,对基因调控可能起重要作用,因此,MITE正逐渐成为基因和基因组进化及生物多样性研究的一种重要工具.本文综述了植物基因组MITE的结构、分类、活性及其应用研究进展.     

苏云金芽孢杆菌转座因子研究进展

近年来的研究发现苏云金芽孢杆菌转座因子和许多毒力因子可能是紧密联系的。由于转座因子的特殊性质,使它们在现代农业生物技术中有着广泛的应用前景,科学家对苏云金芽孢杆菌转座因子的研究也在不断深入。本文主要针对苏云金芽孢杆菌转座因子的研究进展进行综述,并对发展前景进行展望。