首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6篇
  免费   0篇
  2011年   1篇
  2005年   1篇
  2002年   1篇
  2000年   1篇
  1958年   1篇
  1956年   1篇
排序方式: 共有6条查询结果,搜索用时 15 毫秒
1
1.
The relationships between Dactylorhiza romana and D. saccifera from southern Italy were analysed. These two species, both with 2 n = 2 x = 40 chromosomes and belonging to different sections of the genus, were distinguishable on the basis of karyotype structure and heterochromatin amounts and distribution. Their C-banded karyotypes differed considerably. D. saccifera showed most chromosomes with banded regions in the short arms, whereas in D. romana the bands were located mostly at telomeric regions of longer arms. Several individuals of D. romana had one or two very large heterochromatic supernumerary chromosomes. Based on evidence resulting from karyotype structure and heterochromatin distribution in the two species and on the genetic distances derived from the comparison of ITS sequences, it is suggested that D. romana represents a primitive form with respect to D. saccifera and is a possible intermediate step in the evolution of the genus Dactylorhiza from the 42-chromosome Orchis group. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 138 , 85–91.  相似文献   
2.
3.
Karyotype structures and heterochromatin distribution in representative taxa of the genus Ophrys are compared, based on Feulgen-stained and banded somatic metaphase chromosomes. The karyotypes of Ophrys iricolor , O. lupercalis , O. caesiella , O. lutea , O. lunulata , O. x. tardans , O. apifera , O. praecox , O. lacaitae and O. insectifera are described for the first time. The karyological analyses indicate the relationships among the species with respect to asymmetry indices and heterochromatin content. Chromosomal differences have been helpful in clarifying the taxonomic position of Ophrys species that do not have clear affinities. The representative species of Araniferae , Fuciflorae and Ophrys sections exhibited the most asymmetrical karyotypes, while chromosome complements of the O. fusca–O. lutea group, of O. tenthredinifera and of O. bombyliflora proved to be less asymmetrical. Weakly heterochromatic chromosomes, with heterochromatin present mostly in thin centromeric bands, characterize Ophrys C-banded karyotypes. Chromomycin A3 (CMA) staining revealed that the analysed species exhibit a weak pattern of CMA+ bands at centromeric, intercalary or telomeric regions. No DAPI bright blocks were observed. The significance of the karyological data is discussed with regard to the relationships between the analysed species. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 87–99.  相似文献   
4.
5.
Background: The rapid pace of progress in medical research, the consequent need for the timely transfer of new knowledge into practice, and the increasing need for ethics support, is making the work of Ethics Committees (ECs) ever more complex and demanding. As a response, ECs in many countries exhibit large variation in number, mandate, organization and member competences. This cross‐sectional study aims to give an overview of the different types of activities of Italian ECs and favour discussion at a European level. Methods: A questionnaire was emailed to all Italian Ethics Committees contained in the national Registry of the Ministry of Health, enquiring whether the EC was conducting, or planning to conduct, 4 specific activities. A telephone interview was conducted to determine reasons for failure to respond. Results: Response rate was 53% (101 respondents out of 191). 20% of ECs restrict their responsibilities to research protocol review, 25% also offer ethical consultation to institutions, support on individual health care decisions and promotes educational initiatives, while the remaining 50% conduct a few of the examined activities to varying degrees. Large variation was observed across different types of hosting institutions and geographical locations. Conclusions: A common European model should be developed, defining EC functions, member selection modalities, necessary member competences, decision‐making criteria and measures for work verification. In the absence of sound empirical evidence, it would be interesting to study the effectiveness and efficiency of the different existing models.  相似文献   
6.
Giemsa C-banding is utilized for the first time to characterize eight taxa of the genus Serapias . Heterochromatin distribution indicated that the Serapias species form a very homogeneous group. All the species possess chromosome pairs with similar heterochromatin patterns. C-banding showed conspicuous bands located around the centromeres, with some het-erochromatic short arms. There was more heterochromatin in S. apulica and S. nurrika than in the other taxa. Extensive centromeric heterochromatin may indicate recent structural rearrangements in the chromosome complement. Taken altogether, karyomorphology indicates a rather recent origin for the genus Serapias , which might also account for the small amount of interspecific variation observed.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号