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1.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献
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Identification of the signalling molecules involved in mesoderm formation in amphibian embryos still presents problems. None of the original candidates, such as activin, have been definitively ruled out, and the new factors, such as the nodal-related genes, have come on to the scene. Of the original candidates, activin has been definitively shown to act as a morphogen, whereas bone morphogenetic protein (BMP)-4 has emerged as a ventral inducer and an inhibitor of neural differentiation. The effects of BMP-4 are antagonized by chordin, a molecule related to the product of the Drosophila gene short gastrulation. 相似文献
5.
PJS Amaral LFM Finotelo EHC De Oliveira A Pissinatti CY Nagamachi JC Pieczarka 《BMC evolutionary biology》2008,8(1):169
Background
Chromosomal painting, using whole chromosome probes from humans and Saguinus oedipus, was used to establish karyotypic divergence among species of the genus Cebus, including C. olivaceus, C. albifrons, C. apella robustus and C. apella paraguayanus. Cytogenetic studies suggested that the species of this genus have conservative karyotypes, with diploid numbers ranging from 2n = 52 to 2n = 54. 相似文献6.
7.
Ants are powerful model systems for the study of cooperation and sociality. In this review, we discuss how recent advances in ant genomics have contributed to our understanding of the evolution and organization of insect societies at the molecular level. 相似文献
8.
Benjamin Drew Rockett Mark Melton Mitchel Harris Lance C. Bridges Saame Raza Shaikh 《The Journal of nutritional biochemistry》2013,24(11):1810-1816
Fish oil-enriched long chain n-3 polyunsaturated fatty acids disrupt the molecular organization of T-cell proteins in the immunological synapse. The impact of fish oil derived n-3 fatty acids on antigen-presenting cells, particularly at the animal level, is unknown. We previously demonstrated B-cells isolated from mice fed with fish oil-suppressed naïve CD4+ T-cell activation. Therefore, here we determined the mechanistic effects of fish oil on murine B-cell major histocompatibility complex (MHC) class II molecular distribution using a combination of total internal reflection fluorescence, Förster resonance energy transfer and confocal imaging. Fish oil had no impact on presynaptic B-cell MHC II clustering. Upon conjugation with transgenic T-cells, fish-oil suppressed MHC II accumulation at the immunological synapse. As a consequence, T-cell protein kinase C theta (PKCθ) recruitment to the synapse was also diminished. The effects were independent of changes in B-T cell adhesion, as measured with microscopy, flow cytometry and static cell adhesion assays with select immune ligands. Given that fish oil can reorganize the membrane by lowering membrane cholesterol levels, we then compared the results with fish oil to cholesterol depletion using methyl-B-cyclodextrin (MβCD). MβCD treatment of B-cells suppressed MHC II and T-cell PKCθ recruitment to the immunological synapse, similar to fish oil. Overall, the results reveal commonality in the mechanism by which fish oil manipulates protein lateral organization of B-cells compared to T-cells. Furthermore, the data establish MHC class II lateral organization on the B-cell side of the immunological synapse as a novel molecular target of fish oil. 相似文献
9.
JA Williams SE Batten M Harris BD Rockett SR Shaikh W Stillwell SR Wassall 《Biophysical journal》2012,103(2):228-237
Omega-3 polyunsaturated fatty acids (n-3 PUFA), enriched in fish oils, are increasingly recognized to have potential benefits for treating many human afflictions. Despite the importance of PUFA, their molecular mechanism of action remains unclear. One emerging hypothesis is that phospholipids containing n-3 PUFA acyl chains modify the structure and composition of membrane rafts, thus affecting cell signaling. In this study the two major n-3 PUFA found in fish oils, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, are compared. Using solid-state (2)H NMR spectroscopy we explored the molecular organization of 1-[(2)H(31)]palmitoyl-2-eicosapentaenoylphosphatidylcholine (PEPC-d(31)) and 1-[(2)H(31)]palmitoyl-2-docosahexaenoylphosphatidylcholine (PDPC-d(31)) in mixtures with sphingomyelin (SM) and cholesterol (chol). Our results indicate that whereas both PEPC-d(31) and PDPC-d(31) can accumulate into SM-rich/chol-rich raftlike domains, the tendency for DHA to incorporate into rafts is more than twice as great as for EPA. We propose that DHA may be the more bioactive component of fish oil that serves to disrupt lipid raft domain organization. This mechanism represents an evolution in the view of how PUFA remodel membrane architecture. 相似文献
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