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排序方式: 共有79条查询结果,搜索用时 31 毫秒
21.
Th. J. L. van Hintum I. W. Boukema D. L. Visser 《Genetic Resources and Crop Evolution》1996,43(4):343-349
Summary To reduce the number of accessions in the Brassica oleracea collection of the Centre for Genetic Resources The Netherlands (CGN) groups of accessions were bulked. Accessions in a group were selections from the same landrace or old variety, and were chosen, with the help of crop experts, on the basis of their history and morphology. Since this approach was received rather sceptically in the genebank community, a genetical analysis of some of the groups and their components (named varieties) was made to justify the procedures. A selection of white cabbage and Brussels sprouts, representing two crop types of B. oleracea, was made: eleven white cabbage groups comprising 43 components, and nine Brussels sprouts groups comprising 24 components. Each group and all of its components were described on the basis of electrophoresis of nine isoenzymes on 30 plants. Most components were rightly classified; 16 percent were misclassified. All these misclassifications were within similar groups. It could be concluded that pooling of the components included in this study was justified. In two cases the isozymic patterns suggested that the groups could even have been larger. Only in the case of the two groups of Brussels sprouts Bedfordshire this was a real option. In the other case involving the white cabbage groups Langedijker Bewaar Gewoon, Langedijker Bewaar Graag and Late Herfstdeen this was not an option since these landraces, although having a common genetic background, clearly have a distinct identity as defined by morphology and history.
Editorial footnote: We will encourage the publication of further results of research programs in our journal referring to such often controversially discussed concepts, and would appreciate if collections of crops with different breeding systems could be analysed in this respect. 相似文献
22.
本文以图腾图书馆集成管理系统为例,分析馆藏期刊书目数据重复的不利影响及产生的原因,并提出解决和预防数据重复的对策和方法,以期对期刊书目数据库建设有所帮助。 相似文献
23.
Horizontal starch-gel electrophoresis was used to study crude enzyme extraction from young leaves of 234 clones of Populus tomentosa Carr. selected from nine provenances in North China. Ten enzyme systems were resolved. One hundred and fifty-six clones showing
unusual allozyme band patterns at locus Mdh-1 were found. Three allozyme bands at locus Mdh-1 were 9:6:1 in concentration. Further studies on the electrophoretic patterns of ground mixed pollen extraction of 30 male
clones selected at random from the 156 clones were conducted and it was found that allozyme bands at locus Mdh-1 were composed of two dark-stained bands and a weak band. Only one group of the malate dehydrogenase (MDH) zymogram composed
of two bands was obtained from the electrophoretic segregation of pollen leachate of the same clones. A comparison of the
electrophoretic patterns one another suggested that the locus Mdh-1 coding malate dehydrogenase in diploid species of P. tomentosa was duplicated. The duplicate gene locus possessed three same alleles and was located in mitochondria. The locus duplication
of alleles coding malate dehydrogenase in P. tomentosa was discovered and reported for the first time.
[Supported by the “Tenth Five-year Plan” National Key Project in Science and Technology (Grant No. 2002BA515B0303) and the
National “863” Project (Grant No. 2002AA241071)] 相似文献
24.
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to arylalkylamines, including indolethylamines and phenylethylamines. Multiple aanats are present in teleost fish as a result of whole genome and gene duplications. Fish aanat1a and aanat2 paralogs display different patterns of tissue expression and encode proteins with different substrate preference: AANAT1a is expressed in the retina, and acetylates both indolethylamines and phenylethylamines; while AANAT2 is expressed in the pineal gland, and preferentially acetylates indolethylamines. The two enzymes are therefore thought to serve different roles. Here, the molecular changes that led to their specialization were studied by investigating the structure-function relationships of AANATs in the gilthead seabream (sb, Sperus aurata). Acetylation activity of reciprocal mutated enzymes pointed to specific residues that contribute to substrate specificity of the enzymes. Inhibition tests followed by complementary analyses of the predicted three-dimensional models of the enzymes, suggested that both phenylethylamines and indolethylamines bind to the catalytic pocket of both enzymes. These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis. This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles. 相似文献
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为明确重大入侵性害虫草地贪夜蛾Spodoptera frugiperda CRAL_TRIO结构域基因的功能,利用同源比对法鉴定该害虫基因组中的CRAL_TRIO结构域基因,利用系统进化树和基因染色体定位探究其进化关系,使用数字基因表达谱分析其在不同发育阶段的表达情况,并采用反转录PCR技术分析19个CRAL_TRIO结构域基因在雌雄成虫不同组织中的表达特征。结果显示,从草地贪夜蛾基因组中鉴定到46个CRAL_TRIO结构域基因,所编码的氨基酸序列存在典型CRAL_TRIO结构域,且该结构域中有8个保守的氨基酸位点。系统进化树和基因染色体定位分析表明,多数草地贪夜蛾CRAL_TRIO结构域基因通过基因复制进化而来。基因表达谱分析发现,草地贪夜蛾CRAL_TRIO结构域基因在不同发育阶段的表达可聚为2组,其中一组在幼虫前期高表达,另一组在6龄幼虫期、蛹期和成虫期高表达。挑选验证的CRAL_TRIO结构域基因大部分在触角和脑中高表达,有2个基因在触角中特异性表达,部分在复眼中具有较高的表达量,表明这些CRAL_TRIO结构域基因在草地贪夜蛾嗅觉和视觉行为调控中起重要作用。 相似文献
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28.
图书馆编目查重的本土实证——ISBN号查重过程中存在的问题及解决方案 总被引:2,自引:0,他引:2
张丽萍 《农业图书情报学刊》2009,21(1):77-80
分编图书,查重是关键环节,选择适宜的查重途径是基础,通过选取ISBN查重、题名查重、责任者查重这3种最常用的检索方法,论述了查重在图书编目中的重要性,并结合实例,对ISBN号在查重工作中容易出现的问题进行了详细分析,提出了应对措施。 相似文献
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30.
根结线虫属(Meloidogyne spp.)是专性内寄生物,寄主范围广,全球分布,给世界农业生产造成严重为害。生殖方式主要有孤雌生殖和两性融合。系统发育学研究指出,种间杂交可能在根结线虫多样化的进程中起着重要作用。越来越多的证据表明,基因组范围内的序列重复和水平基因转移为根结线虫的多样性提供了遗传基础。南方根结线虫(Meloidogyne incognita)和北方根结线虫(Meloidogyne hapla)基因组测序的完成和注释也为研究根结线虫的多样性提供了重要线索。根结线虫的多样性给鉴定和防治工作带来了巨大挑战,需要寻找更加有效的方法。 相似文献