共查询到20条相似文献，搜索用时 15 毫秒
1.
The climatic and environmental changes associated with the last glaciation (90,000 to 10,000 years before the present; 90 to 10 ka B.P.) are an important example of the effects of global climate change on biological diversity. These effects were particularly marked in Beringia (northeastern Siberia, northwestern North America, and the exposed Bering Strait) during the late Pleistocene. To investigate the evolutionary impact of these events, we studied genetic change in the brown bear, Ursus arctos, in eastern Beringia over the past 60,000 years using DNA preserved in permafrost remains. A marked degree of genetic structure is observed in populations throughout this period despite local extinctions, reinvasions, and potential interspecies competition with the short-faced bear, Arctodus simus. The major phylogeographic changes occurred 35 to 21 ka B.P., before the glacial maximum, and little change is observed after this time. Late Pleistocene histories of mammalian taxa may be more complex than those that might be inferred from the fossil record or contemporary DNA sequences alone. 相似文献
2.
The evolution of sex chromosomes 总被引：42，自引：0，他引：42
B Charlesworth 《Science (New York, N.Y.)》1991,251(4997):1030-1033
Structurally distinct sex chromosomes (X and Y) are the most familiar mode of genetic sex determination and have evolved independently in many different taxa. The evolutionary paths by which their characteristic properties may have evolved are reviewed. These properties include the failure of X and Y to recombine through much or all of their length, the genetic inertness of much of the Y chromosome, dosage compensation of the activity of X chromosomal loci, and the accumulation of repeated DNA sequences on the Y chromosome. 相似文献
3.
DNA指纹分析在植病真菌群体遗传研究中的应用 总被引：2，自引：0，他引：2
在总结植物病原真菌遗传标记的应用发展过程基础上，着重以重复序列为基础的ＤＮＡ分子标记的应用，综述了近年来ＤＮＡ指纹分析在植物病原真菌群体遗传分析中的应用。还简要讨论了群体遗传分析对植物病理学的深远影响 相似文献
4.
5.
Tumor DNA structure in plant cells transformed by A. tumefaciens 总被引：25，自引：0，他引：25
P Zambryski M Holsters K Kruger A Depicker J Schell M Van Montagu H M Goodman 《Science (New York, N.Y.)》1980,209(4463):1385-1391
Crown gall tumors are induced in plants by infection with the soil bacterium Agrobacterium tumefaciens. Because the tumor induction involves transfer of a portion of the tumor-inducing (Ti) plasmid DNA from the bacterium to the plant cells, this system is of interest for the study of genetic exchange as well as tumor induction. The boundaries of the transferred DNA (T-DNA) have been cloned from transformed plant cells of tobacco. Detailed mapping with restriction enzymes and nucleotide sequence analysis of two independent clones were used to study the molecular structure of the ends of the T-DNA. One clone contains the two ends of the T-DNA joined together; the other contains one end of the T-DNA joined to repetitive plant DNA sequences. These studies provide direct evidence that the T-DNA can be integrated into the plant genome. In addition, the data suggest that in the plant, T-DNA can be tandemly repeated. Sequence analysis of the junction of crown gall clone 1 reveals several direct repeats as well as an inverted repeat; these structures may be involved in the transfer of the DNA from Agrobacterium to plant cells. 相似文献
6.
7.
Asara JM Schweitzer MH Freimark LM Phillips M Cantley LC 《Science (New York, N.Y.)》2007,316(5822):280-285
Fossilized bones from extinct taxa harbor the potential for obtaining protein or DNA sequences that could reveal evolutionary links to extant species. We used mass spectrometry to obtain protein sequences from bones of a 160,000- to 600,000-year-old extinct mastodon (Mammut americanum) and a 68-million-year-old dinosaur (Tyrannosaurus rex). The presence of T. rex sequences indicates that their peptide bonds were remarkably stable. Mass spectrometry can thus be used to determine unique sequences from ancient organisms from peptide fragmentation patterns, a valuable tool to study the evolution and adaptation of ancient taxa from which genomic sequences are unlikely to be obtained. 相似文献
8.
微卫星(microsatellites)或简单序列重复(simple sequence repeats,SSRs)是以1～6个碱基为基本单元的串联重复序列,具有含量丰富、多态性高、共显性和检测方法简单等优点,是研究植物遗传多样性的优异的分子标记之一,已被用于多种植物的遗传多样性研究。概述了微卫星DNA标记的原理及特点,介绍了其实验技术方法及发展,探讨了其在植物遗传多样性中的应用和发展前景。 相似文献
9.
Three distinct genes in human DNA related to the transforming genes of mammalian sarcoma retroviruses 总被引：9，自引：0，他引：9
F Wong-Staal R Dalla-Favera G Franchini E P Gelmann R C Gallo 《Science (New York, N.Y.)》1981,213(4504):226-228
Southern blot hybridization was used to identify human and other vertebrate DNA sequences that were homologous to cloned DNA fragments containing the oncogenic nucleic acid sequences of three different type C mammalian retroviruses (simian sarcoma virus, the Snyder-Theilen strain of feline sarcoma virus, and the Harvey strain of murine sarcoma virus). Each onc gene counterpart has a single genetic locus, which probably contains non-onc intervening sequences. The human DNA sequences may represent genes important to cell growth or cell differentiation, or both. Their identification and isolation may allow elucidation of their role in these processes and in neoplasias. 相似文献
10.
11.
植物线粒体结构基因组研究进展 总被引：2，自引：0，他引：2
植物线粒体基因组具有复杂的结构特征:基因组200~2 400 kb不等,变化大、重组频繁,存在水平基因迁移现象等。基因组中既含有非常保守的功能基因,也存在高度变异的基因间区序列。大量研究表明,线粒体基因组是植物细胞质雄性不育因子的载体。综述了近年来植物线粒基因组结构特征、基因组成和热点研究的进展,为进一步深入研究植物细胞质雄性不育的分子机理,并为胞质雄性不育三系杂交种选育、作物杂种优势利用提供理论指导。 相似文献
12.
从泰山土壤中分离获得1株细菌4’531,对其进行了形态特征观察、生理生化特征测定及16S rDNA序列分析,并构建了包括其在内的10株相关种属菌株的系统发育树,最后研究了其对烟赤星病(Alternariaalternate)、黄瓜枯萎病菌(Fusarium oxysporum)、棉立枯病菌(Rhizoctonia solani)3种植物病原真菌的拮抗作用。结果表明,4’531菌株属于类芽孢杆菌属(Paenibacillus),与其亲缘关系较近菌株Paenibacillus polymyxa(AJ320493)的同源性达98%;结合形态和生理生化特征,鉴定该菌株为多粘类芽孢杆菌(Paenibacillus polymyxa),该菌株的16S rDNA序列已在GenBank中注册,登录号为DQ279739;4’531菌株对3种供试植物病原真菌均有明显的拮抗作用。 相似文献
13.
32个菊花近缘种属植物耐盐性筛选 总被引：5，自引：2，他引：3
【目的】确定菊花耐盐种质的筛选方法,并以2个栽培菊花品种为对照,对30份菊花近缘种属野生资源进行耐盐性筛选,为耐盐菊花新品种选育提供耐盐种质。【方法】在Hoagland营养液水培条件下,分别设置5个浓度NaCl(0、40、80、120、160、200mmol·L-1)对4份菊花近缘种属植物进行处理,根据单株受害叶面积比率的差异,确定适宜的筛选浓度;在此筛选浓度下对32份材料进行胁迫处理,通过建立受害程度与胁迫时间的数学回归模型,利用回归方程分别求出材料单株受害叶面积达50%所需用时间,以此进行耐盐性排序,并与其它叶片形态受害指标的筛选结果相比较,采用系统聚类法综合各项指标评价各材料耐性。【结果】耐盐筛选适宜浓度为120mmol·L-1,在此胁迫浓度下,各指标的变异系数较大,依据不同指标的耐盐筛选结果间相关性较高;建立了3类共32个回归方程,各方程的回归效果良好。【结论】以叶片形态症状为依据可以对菊花近缘属植物的耐盐性进行快速、有效筛选,根据聚类结果将32份耐盐性材料分为极强、强、中等、敏感4个级别,芙蓉菊、牡蒿、达磨菊耐盐性极强;菊蒿、大岛野路菊耐盐性强;滨菊、黄金艾等7份材料的耐盐性中等,栽培菊、紫花野菊、小红菊、毛华菊、甘菊等20份材料对盐胁迫敏感。 相似文献
14.
驴生长激素基因的克隆与分析 总被引：1，自引：0，他引：1
【目的】克隆驴生长激素基因DNA和cDNA的全序列,分析其序列和cDNA编码的蛋白序列特征及其在不同物种中的遗传差异。【方法】根据不同物种同一基因序列的同源性比对结果设计引物,应用RT-PCR和PCR 技术克隆基因,用生物信息学方法对获得的DNA和cDNA及推定的氨基酸序列进行分析。【结果】从驴肝组织和血液中分别得到驴GH基因全序列1 928 bp和包括完整的编码区的cDNA序列706 bp,两者序列比对后证明驴GH基因DNA序列由5个外显子和4个内含子组成,编码216个氨基酸的GH前体蛋白,其中包括26个氨基酸的信号肽和190个氨基酸的成熟肽。序列比较结果表明,驴GH基因的序列与马同源性最高,启动子不是哺乳动物的典型TATA盒,而是CATA盒,该基因在进化过程中是保守的。【结论】从驴肝组织和血液中克隆了GH基因DNA和cDNA,DNA序列在1 267位的C→G可能影响到驴和马生长发育的差异,为下一步驴GH基因的表达调控、进化和多态性分析奠定了基础。 相似文献
15.
16.
基于AFLP的菊属、亚菊属及其近缘属的属间关系 总被引：2，自引：0，他引：2
【目的】由于研究材料、地理分布等条件的限制,菊属(Dendranthema)、亚菊属(Ajania)及其近缘属的属间关系未得到很好解决。核糖体ITS区和叶绿体trnL/trnF间区等相关分子序列解析用于研究植物系统进化具有较大优势,但在菊属及其近缘属等相关类群间存在信息位点低的问题,而AFLP标记以其高多态性的优点在亲缘关系很近类群的系统演化研究中表现出一定的优势,因此本研究利用AFLP技术对菊属、亚菊属及其近缘属的属间关系进行研究,旨在分析和探讨菊属、亚菊属及其近缘属的系统关系,同时为菊花(D.×grandiflorum)等材料的遗传育种提供参考。【方法】利用9对荧光标记引物对东亚蒿亚族菊属、亚菊属及其近缘类群共50个分类单元进行AFLP分析,同时分别利用SPSS11.0软件采用非加权平均数UPGMA方法和PAUP*4.0b10软件采用最大简约法进行聚类分析。【结果】AFLP分析共获得1695个多态性条带。根据相似性系数,无论是整个蒿亚族及其近缘类群内部,还是菊属、亚菊属内部,均表现出较高的遗传多样性,种间分化明显。【结论】无论是UPGMA聚类分析结果还是构建的最大简约树,AFLP结果均将菊属和Arctanthemum先聚为一亚分支,各自形成两个种群,各自种群包含亚菊属的个别类群;亚菊属的大部分类群和太行菊属(Opisthopappus)形成另一亚分支,与菊属亚分支互为姐妹群形成菊属-亚菊属大分支。这说明菊属和亚菊属可能是由共同的祖先类群平行演化而来,其中亚菊属的多花亚菊(A.myriantha)、铺散亚菊(A.khartensis)等与菊属亲缘关系较近,而原产日本的矶菊(A.pacifica)、盐菊(A.shiwogiku)等是亚菊属中较进化类型;太行菊属的系统地位可能更接近于蒿亚族;短舌菊属(Brachanthemum)则被排除于菊属群之外。柳叶亚菊(A.salicifolia)、异叶亚菊(A.variifolia)等应从亚菊属中分离出来,支持单列成栎叶菊属(Phaeostigma)。 相似文献
17.
18.
19.
Day PR 《Science (New York, N.Y.)》1977,197(4311):1334-1339
Cell cultures of crop plants provide new opportunities to recover induced mutations likely to increase crop yield. Approaches include regulating respiration to conserve carbon fixed by photosynthesis, and increasing the nutritive value of seed protein. They depend on devising selecting conditions which only desired mutant cells can survive. Protoplast fusion offers some promise of tapping sources of genetic variation now unavailable because of sterility barriers between species and genera. Difficulties in regenerating cell lines from protoplasts, and plants from cells, still hamper progress but are becoming less severe. Recombinant DNA techniques may allow detection and selection of bacterial cell lines carrying specific DNA sequences. Isolation and amplification of crop plant genes could then lead to ways of transforming plants that will be useful to breeders. 相似文献
20.
植物病毒群体遗传学的2个中心任务是定量描述病毒种群内的遗传变异及阐明该变异的机制.植物病毒自然种群遗传结构通常包括1-2种优势的序列变异类型和一些低频率的序列变异类型,即具有准种遗传结构特征.植物病毒种群遗传多样性水平和病害暴发以及流行时间有一定的相关性.另外,植物病毒种群遗传结构中还存在超群种群类型.一些生物学特性可能取决于准种内的不同变种间的相互作用.如决定适应能力、寄主范围及致病性变异等.植物寄主—昆虫介体—病毒三者间的协同进化关系是植物病毒种群遗传结构保存相对稳定的主要因素.描述植物病毒种群遗传结构特征为构建更有效的病害防治策略提供了依据. 相似文献