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461.
Evolutionary relationships of human populations on a global scale 总被引:28,自引:2,他引:26
Using gene frequency data for 29 polymorphic loci (121 alleles), we
conducted a phylogenetic analysis of 26 representative populations from
around the world by using the neighbor-joining (NJ) method. We also
conducted a separate analysis of 15 populations by using data for 33
polymorphic loci. These analyses have shown that the first major split of
the phylogenetic tree separates Africans from non-Africans and that this
split occurs with a 100% bootstrap probability. The second split separates
Caucasian populations from all other non-African populations, and this
split is also supported by bootstrap tests. The third major split occurs
between Native American populations and the Greater Asians that include
East Asians (mongoloids), Pacific Islanders, and Australopapuans (native
Australians and Papua New Guineans), but Australopapuans are genetically
quite different from the rest of the Greater Asians. The second and third
levels of population splitting are quite different from those of the
phylogenetic tree obtained by Cavalli- Sforza et al. (1988), where
Caucasians, Northeast Asians, and Ameridians from the Northeurasian
supercluster and the rest of non- Africans form the Southeast Asian
supercluster. One of the major factors that caused the difference between
the two trees is that Cavalli-Sforza et al. used unweighted pair-group
method with arithmetic mean (UPGMA) in phylogenetic inference, whereas we
used the NJ method in which evolutionary rate is allowed to vary among
different populations. Bootstrap tests have shown that the UPGMA tree
receives poor statistical support whereas the NJ tree is well supported.
Implications that the phylogenetic tree obtained has on the current
controversy over the out-of-Africa and the multiregional theories of human
origins are discussed.
相似文献
462.
内蒙古蝗总科Acridoidea区系组成及其区域分布的研究 总被引:1,自引:0,他引:1
作者1983~1989连续七年,对内蒙古高原本部、边缘山地、外沿平原和高原的不同类型草原植被进行考察并广泛采集昆虫标本;其中,获蝗总科标本计34613号,经鉴定有5科13亚科40属95种(包括亚种)。文中分析了各蝗种的区系地理成分、种属分配,讨论了三大不同地形区域及其所属13个不同自然地区的蝗虫区系组成及其区域分布特性。提出了“阿拉善蒙古种”应被视为是一个独立的区系地理成分,以及内蒙古东部大兴安岭森林及森林草原地区和西部的阿拉善荒漠地区应被视为是两个各具湿冷或干热——截然不同生态地理特征的蝗虫区系起源地。最后作者对内蒙古蝗总科区系的地史演化过程进行了初步探讨。 相似文献
463.
Evolution of the major histocompatibility complex: independent origin of nonclassical class I genes in different groups of mammals 总被引:22,自引:3,他引:19
The class I major histocompatibility complex genes are composed of classical and nonclassical genes, the latter being largely nonfunctional. To understand the evolutionary relationships of the two groups of class I genes, a phylogenetic analysis of DNA sequences was conducted using 45 genes from six mammalian and one avian species. The results indicate that nonclassical genes in one species are more closely related to classical genes from the same species than to nonclassical genes from a species belonging to a different order or family. This indicates that the differentiation of classical and nonclassical genes occurs rather rapidly in the genome. Classical genes are apparently duplicated with a high frequency in the evolutionary process, and many of the duplicated genes seem to degenerate into nonclassical genes as a result of deleterious mutation. The nonclassical Qa genes in the mouse have sequences homologous to regulatory sequences involved in the universal expression of classical class I genes, but they have accumulated numerous nucleotide substitutions in these sequences. The pattern of nucleotide substitution in nonclassical genes is different from that in classical genes. In nonclassical genes, the rate of nonsynonymous substitution is higher in the antigen recognition site than in other gene regions, as is true of classical genes. However, unlike the case of classical genes, the nonsynonymous rate does not always exceed the synonymous rate in the antigen recognition site. Nonclassical proteins further differ from classical proteins in having amino acid replacements in conserved antigen recognition site positions. These observations are consistent with the hypothesis that nonclassical genes have originated from classical genes but have lost classical class I function because of deleterious mutation. 相似文献
464.
Kazuhiko Nishide Takahito Nishikata Noriyuki Satoh 《Development, growth & differentiation》1989,31(6):595-600
In spite of extensive knowledge on the structure and function of ascidian blood cells, little is known about their embryological origin. In the present investigation, the developmental fate of trunk lateral cells (TLCs) was explored using a specific monoclonal antibody. TLCs comprise a group of undefined embryonic cells of the ascidian Halocynthia roretzi , which arise from the A7.6 blastomeres of a 64-cell embryo. The antigenicity first appeared at the middle tailbud stage in a pair of TLC-clusters situated lateral to the brain stem of the bilaterally symmetrical embryo. The position and number of stained cells did not change during later embryogenesis until hatching. After hatching, the stained cells were found in the entire trunk region of the swimming larva. After metamorphosis, cells that expressed the antigen were present within the coelom and within the tunic layer of the juvenile. In addition, the antibody stained adult basophilic blood cells. These observations suggest a relationship of this group of embryonic cells with the prospective blood forming mesenchymal cells. 相似文献
465.
Shinji Goto Miho Kawakatsu Shin-ichi Izumi Yoshishige Urata Kan Kageyama Yoshito Ihara Takehiko Koji Takahito Kondo 《Free radical biology & medicine》2009,46(10):1392-1403
Glutathione S-transferases (GSTs) are multifunctional enzymes involved in the protection of cellular components against anti-cancer drugs or peroxidative stress. Previously we found that GST π, an isoform of the GSTs, is transported into the nucleus. In the present study, we found that GST π is present in mitochondria as well as in the cytosol and nucleus in mammalian cell lines. A construct comprising the 84 amino acid residues in the amino-terminal region of GST π and green fluorescent protein was detected in the mitochondria. The mutation of arginine to alanine at positions 12, 14, 19, 71, and 75 in full-length GST π completely abrogated the ability to distribute in the mitochondria, suggesting that arginine, a positively charged residue, is required for the mitochondrial transport of GST π. Chemicals generating reactive oxygen species, such as rotenone and antimycin A, decreased cell viability and reduced mitochondrial membrane potential. The overexpression of GST π diminished these changes. GST π-targeting siRNA abolished the protective effect of GST π on the mitochondria under oxidative stress. The findings indicate that the peptide signal is conducive to the mitochondrial localization of GST π under steady-state conditions without alternative splicing or posttranslational modifications such as proteolysis, suggesting that GST π protects mitochondria against oxidative stress. 相似文献
466.
Keishi Takano Yasushi Ishikawa Hidetoshi Mikami Seiki Igarashi Shuji Hino Takahito Yoshioka 《Limnology》2008,9(3):213-218
Fungal infection of the filamentous cyanobacterium Anabaena smithii was observed in Lake Shumarinai in 2004–2006. Two fungal species were found to parasitize the specialized cells of A. smithii. These fungi might not correspond to the chytrid species that the previous studies reported as the parasites for Anabaena species. One fungus showed selective attachment to the akinete (akinete type). The filaments parasitized by this fungus increased
in August 2004 and October 2006, when akinete and filament densities also increased. The maximum percentage of parasitized
filaments was 3.2% of all filaments in October 2006. The other fungus was usually attached to the heterocyst (heterocyst type).
The filaments parasitized by this fungus increased in October from 2004 to 2006. The maximum percentage of parasitized filaments
was 20.6% in October 2004. The biomass of A. smithii was not suppressed by akinete-type fungus because of the low percentage of parasitized filaments. The heterocyst-type fungus
might disturb the nitrogen fixation, but its effect was negligible due to a high concentration of available nitrogen for planktonic
algae in Lake Shumarinai. 相似文献
467.
MEGA2: molecular evolutionary genetics analysis software. 总被引:201,自引:0,他引:201
We have developed a new software package, Molecular Evolutionary Genetics Analysis version 2 (MEGA2), for exploring and analyzing aligned DNA or protein sequences from an evolutionary perspective. MEGA2 vastly extends the capabilities of MEGA version 1 by: (1) facilitating analyses of large datasets; (2) enabling creation and analyses of groups of sequences; (3) enabling specification of domains and genes; (4) expanding the repertoire of statistical methods for molecular evolutionary studies; and (5) adding new modules for visual representation of input data and output results on the Microsoft Windows platform. AVAILABILITY: http://www.megasoftware.net. CONTACT: s.kumar@asu.edu 相似文献
468.
Hahismoto S Yazawa S Asao T Faried A Nishimura T Tsuboi K Nakagawa T Yamauchi T Koyama N Umehara K Saniabadi AR Kuwano H 《Glycoconjugate journal》2008,25(6):531-544
Chemically synthesized sugar-cholestanols with mono-, di-, and tri-saccharides attached to cholestanol showed strong inhibiting activity against the proliferation of colorectal and gastric cancer cells. In contrast, cholestanol without sugar moieties was totally ineffective. Furthermore, when cancer cells were exposed to GlcNAcRbetacholestanol (R=(-) or beta1-3Gal), the compound was rapidly taken up via the lipid rafts/microdomains on the cell surface. The uptake of sugar-cholestanol in mitochondria increased gradually and was followed by the release of cytochrome c from mitochondria and the activation of apoptotic signals through the mitochondrial pathway and the caspase cascade, leading to apoptotic cell death, characterized by DNA ladder formation and nuclear fragmentation. Additionally, the examination of GlcNAcRbetacholestanol in a mouse model of peritoneal dissemination showed a dramatic reduction of tumor growth (P < 0.003) and prolonged mouse survival time (P<0.0001). Based on these observations, we believe that the sugar-cholestanols described here have clinical potential as novel anticancer agents. 相似文献
469.
So S Chijiwa T Ikeda N Nobuhisa I Oda-Ueda N Hattori S Ohno M 《Journal of molecular evolution》2008,66(3):298-307
A cDNA encoding a novel phospholipase A2 (PLA2) inhibitor (PLI) was isolated from a Protobothrops flavoviridis snake (Tokunoshima island, Japan) liver cDNA library. This cDNA encoded a signal peptide of 19 amino acids followed by a
mature protein of 181 amino acids. Its N-terminal amino acid sequence was completely in accord with that of a PLI, named PLI-II,
previously found in P. flavoviridis serum. PLI-II showed a high similarity in sequence to the B subtype of γPLI, denoted γPLI-B, isolated from Agkistrodon blomhoffii siniticus serum. Thus, PLI-II is P. flavoviridis serum γPLI-B. Since PLI-I, previously isolated from P. flavoviridis serum, can be assigned as γPLI-A, P. flavoviridis serum contains both A and B subtypes of γPLI. Phylogenetic analysis of γPLIs from the sera of various kinds of snakes, Elapinae,
Colubrinae, Laticaudinae, Acanthophiinae, Crotalinae, and Pythonidae, based on the amino acid sequences revealed that A and
B subtypes of γPLIs are clearly separated from each other. It was also found that phylogenetic topologies of γPLIs are in
good agreement with speciation processes of snakes. The BLAST search followed by analyses with particular Internet search
engines of proteins with Cys/loop frameworks similar to those of PLI-II and PLI-I revealed that γPLI-Bs, including PLI-II
and PLI-II-like proteins from mammalian sources, form a novel PLI-II family which possesses the common Cys/loop frameworks
in the anterior and posterior three-finger motifs in the molecules. Several lines of evidence suggest that PLI-II is evolutionarily
ancestral to PLI-I.
The nucleotide sequence reported in this paper is available from the GenBank/EMBL/DDBJ databases under accession number AB290845. 相似文献
470.
Molecular evolution of the nontandemly repeated genes of the histone 3 multigene family. 总被引:9,自引:0,他引:9
Alejandro P Rooney Helen Piontkivska Masatoshi Nei 《Molecular biology and evolution》2002,19(1):68-75
In some species, histone gene clusters consist of tandem arrays of each type of histone gene, whereas in other species the genes may be clustered but not arranged in tandem. In certain species, however, histone genes are found scattered across several different chromosomes. This study examines the evolution of histone 3 (H3) genes that are not arranged in large clusters of tandem repeats. Although H3 amino acid sequences are highly conserved both within and between species, we found that the nucleotide sequence divergence at synonymous sites is high, indicating that purifying selection is the major force for maintaining H3 amino acid sequence homogeneity over long-term evolution. In cases where synonymous-site divergence was low, recent gene duplication appeared to be a better explanation than gene conversion. These results, and other observations on gene inactivation, organization, and phylogeny, indicated that these H3 genes evolve according to a birth-and-death process under strong purifying selection. Thus, we found little evidence to support previous claims that all H3 proteins, regardless of their genome organization, undergo concerted evolution. Further analyses of the structure of H3 proteins revealed that the histones of higher eukaryotes might have evolved from a replication-independent-like H3 gene. 相似文献