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71.
Ying Cao Jun Adachi Axel Janke Svante Pääbo Masami Hasegawa 《Journal of molecular evolution》1994,39(5):519-527
The phylogenetic relationships among Primates (human), Artiodactyla (cow), Cetacea (whale), Carnivora (seal), and Rodentia (mouse and rat) were estimated from the inferred amino acid sequences of the mitochondrial genomes using Marsupialia (opossum), Aves (chicken), and Amphibia (Xenopus) as an outgroup. The overall evidence of the maximum likelihood analysis suggests that Rodentia is an outgroup to the other four eutherian orders and that Cetacea and Artiodactyla form a clade with Carnivora as a sister taxon irrespective of the assumed model for amino acid substitutions. Although there remains an uncertainty concerning the relation among Artiodactyla, Cetacea, and Carnivora, the existence of a clade formed by these three orders and the outgroup status of Rodentia to the other eutherian orders seems to be firmly established. However, analyses of individual genes do not necessarily conform to this conclusion, and some of the genes reject the putatively correct tree with nearly 5% significance. Although this discrepancy can be due to convergent or parallel evolution in the specific genes, it was pointed out that, even without a particular reason, such a discrepancy can occur in 5% of the cases if the branching among the orders in question occurred within a short period. Due to uncertainty about the assumed model underlying the phylogenetic inference, this can occur even more frequently. This demonstrates the importance of analyzing enough sequences to avoid the danger of concluding an erroneous tree. 相似文献
72.
利用COS7细胞暂时表达系统,研究转译起始序列对EPO-cDNA表达的影响。通过DNA重组技术,构建了原EPO-cDNA表达载体pCSV-EPO(1),其转译起始序列为5'AATTCATGG3'。同时通过定点突变技术,将起始序列改变成5'CCACCATGG3',而构建了另一表达载体PCSV-EPO(2)。后经序列分析证明无误后和前均通过DEAE-dextran法转染COS7细胞上清,测定结果为 相似文献
73.
广东种子植物区系地理成分研究 总被引:20,自引:5,他引:15
广东种子植物区系共有219科1434属4986种。其中:①热带区系成分占有较大的比例,约占非世界属的62.3%,表明广东区系受到热带区系的强烈渗透,次之为亚热带(至亚热带山地)成分约占32.2%,及中国特有分布占5.6%;②以单型属(72属),单种属(585属)和寡种属(562属)占绝对优势,共占85.0%,充分显示了广东区系的古老性和过渡性特点;③从区系组成和植被结构的特征成分来看,以华夏植物区系成分为主,包括:亚热带分布,亚热带山地分布,中国特有分布,东亚—北美间断分布,及一些亚洲热带分布中以亚热带为主的属:④在这些属中有东亚特有属132属,中国特有属75属以及华南—西南—中南半岛特有属68属等;这些属的存在毫无疑问地说明,广东区系是华夏植物区系的核心地区之一,同时也显示了热带区系与亚热带区系有着不可分隔的统一性。 相似文献
74.
Renu Tuteja Narendra Tuteja Franco Lilliu Bruno Bembi Renzo Galanello Antonio Cao Francisco E. Baralle 《Human genetics》1994,94(3):314-315
We report a novel mutation in exon 9 of the glucocerebrosidase gene of a patient with Gaucher disease and of Sardinian origin. 相似文献
75.
The use of PCR to monitor the population abundance of six human intestinal bacterial species in an in vitro semicontinuous culture system 总被引:2,自引:0,他引:2
Rong-Fu Wang Wei-Wen Cao Warren L. Campbell Latrina Hairston Wirt Franklin Carl E. Cerniglia 《FEMS microbiology letters》1994,124(2):229-237
Abstract Six PCR primer sets complementary to the 16S rDNAs (rRNA genes) were developed and shown to be specific for the following anaerobic bacteria: Clostridium clostridiiforme, C. perfringens, C. leptum, Bacteroides vulgatus, B. distasonis , and B. thetaiotaomicron , respectively. These primers were used for PCR to detect and monitor the bacteria in a semicontinuous culture system designed to mimic intestinal microflora in the human gastrointestinal tract. Except for C. perfringens , the five species of Bacteroides and Clostridia present in the in vitro culture system were detected by the PCR, and the titers varied from 10−2 to 10−6 dilutions. The role of azo dye reduction by these bacterial species in the system was examined and discussed. 相似文献
76.
Chunyu Cao Hisao Kurazono Shinji Yamasaki Keiko Kashiwagi Kazuei Igarashi Yoshifumi Takeda 《Microbiology and immunology》1994,38(6):441-447
The gene encoding a Verotoxin 2 variant, VTvp1, was mutated by oligonucleotide-directed site-specific mutagenesis. Among 6 mutant toxins encoded by the mutated genes, E167Q-R170L (glutamic acid at position 167 and arginine at position 170 from N-terminus of the A subunit were replaced by glutamine and leucine, respectively) was found to have markedly decreased activities; inhibition of protein synthesis, Vero cell cytotoxicity and mouse lethality of the purified E167Q-R170L were 1/1,900, 1/125,000 and 1/2,000, respectively, of those of the purified wild-type VT2vp1. Since the antigenic property of the E167Q-R170L was demonstrated to be similar to that of the wild-type VT2vp1 by Ouchterlony double gel diffusion test and by neutralization test of Vero cell cytotoxicity of the VT2vp1, a possibility to use the mutant VT2vp1, E167Q-R170L, as a toxoid is discussed. 相似文献
77.
三褶脉紫菀中的新二萜甙 总被引:1,自引:0,他引:1
三褶脉紫菀(AsterageratoidesTurcz.)系菊科多年生草本植物,遍布全国,是民间常用的中药,有清热解毒、祛痰镇咳的功效[1,2]。化学工作者们曾从其同属植物紫菀(AstertararicusL.f.)中分离到紫菀酮(shionone)、槲皮素(quercetin)、无羁萜(friedelin)、表无羁萜(epifriedelinel)、毛叶醇(lachnophyllol)、乙酸毛叶酯(lachnophyllolacetate)、茴香醚(anethole)以及紫菀三萜皂甙[2—4]… 相似文献
78.
79.
Phylogenetic place of guinea pigs: no support of the rodent-polyphyly hypothesis from maximum-likelihood analyses of multiple protein sequences 总被引:3,自引:2,他引:1
Graur et al.'s (1991) hypothesis that the guinea pig-like rodents have an
evolutionary origin within mammals that is separate from that of other
rodents (the rodent-polyphyly hypothesis) was reexamined by the
maximum-likelihood method for protein phylogeny, as well as by the
maximum-parsimony and neighbor-joining methods. The overall evidence does
not support Graur et al.'s hypothesis, which radically contradicts the
traditional view of rodent monophyly. This work demonstrates that we must
be careful in choosing a proper method for phylogenetic inference and that
an argument based on a small data set (with respect to the length of the
sequence and especially the number of species) may be unstable.
相似文献
80.