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  • 1
    ISSN: 1432-1432
    Keywords: Hominoid phylogeny ; Mitochondrial DNA ; Nucleotide substitutions ; Molecular clock ; Phylogenetic trees ; Divergence times
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Molecular biology has resurrected C. Darwin and T.H. Huxley's question about the origin of humans, but the precise branching pattern and dating remain controversial. To settle this issue, a large amount of sequence information is required. We determined mitochondrial (mt) DNA sequences for five hominoids; pygmy and common chimpanzees, gorilla, orangutan, and siamang. The common region compared with the known human sequence is 4759 by long, encompassing genes for 11 transfer RNAs and 6 proteins. Because of the high substitution rates in mammalian mtDNA and an unprecedentedly large region compared, the sequence differences clearly indicate that the closest relatives to human are chimpanzees rather than gorilla. For dating the divergences of human, chimpanzee, and gorilla, we used only unsaturated parts of sequence differences in which the mtDNA genealogy is not obscured by multiple substitutions. The result suggests that gorilla branched off 7.7 ± 0.7 million years (Myr) ago and human 4.7 ± 0.5 Myr ago; the time difference between these divergences being as long as 3 Myr.
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  • 2
    ISSN: 1432-1432
    Keywords: Molecular clock with variable rate ; Branching order ; Branching date ; Maximum likelihood ; AIC ; Bootstrap probability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Based on mitochondrial DNA (mt-DNA) sequence data from a wide range of primate species, branching order in the evolution of primates was inferred by the maximum likelihood method of Felsenstein without assuming rate constancy among lineages. Bootstrap probabilities for being the maximum likelihood tree topology among alternatives were estimated without performing a maximum likelihood estimation for each resampled data set. Variation in the evolutionary rate among lineages was examined for the maximum likelihood tree by a method developed by Kishino and Hasegawa. From these analyses it appears that the transition rate of mtDNA evolution in the lemur has been extremely low, only about 1/10 that in other primate lines, whereas the transversion rate does not differ significantly from that of other primates. Furthermore, the transition rate in catarrhines, except the gibbon, is higher than those in the tarsier and in platyrrhines, and the transition rate in the gibbon is lower than those in other catarrhines. Branching dates in primate evolution were estimated by a molecular clock analysis of mtDNA, taking into account the rate of variation among different lines, and the results were compared with those estimated from nuclear DNA. Under the most likely model, where the evolutionary rate of mtDNA has been unifrom within a great apes/human calde, human/chimpanzee clustering is preferred to the alternative branching orders among human, chimpanzee, and gorilla.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 41 (1995), S. 359-365 
    ISSN: 1432-1432
    Keywords: Gibbons ; Mitochondrial DNA ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We analyzed the 896 base-pair (bp) mitochondrial DNA (mtDNA) sequences for seven gibbons, representative of three out of four subgenera. The result from our molecular analysis is consistent with previous studies as to the monophyly of subgenusHylobates species, yet the relationship among subgenera remains slightly ambiguous. A striking result of the analysis is the phylogenetic location of Kloss's gibbon (H. klossii). Kloss's gibbon has been considered to be an initial off-shoot of the subgenusHylobates because of its morphological primitiveness. However, our molecular data strongly suggest that Kloss's gibbon speciated most recently within the subgenusHylobates.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 41 (1995), S. 359-365 
    ISSN: 1432-1432
    Keywords: Gibbons ; Mitochondrial DNA ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We analyzed the 896 base-pair (bp) mitochondrial DNA (mtDNA) sequences for seven gibbons, representative of three out of four subgenera. The result from our molecular analysis is consistent with previous studies as to the monophyly of subgenus Hylobates species, yet the relationship among subgenera remains slightly ambiguous. A striking result of the analysis is the phylogenetic location of Kloss's gibbon (H. klossii). Kloss's gibbon has been considered to be an initial off-shoot of the subgenus Hylobates because of its morphological primitiveness. However, our molecular data strongly suggest that Kloss's gibbon speciated most recently within the subgenus Hylobates.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 32 (1991), S. 37-42 
    ISSN: 1432-1432
    Keywords: Nucleotide sequences ; Major noncoding region ; Evolutionary rates ; Molecular clock ; Rate heterogeneity among sites ; Effective proportion of variable sites ; Maximum likelihood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A molecular clock analysis was carried out on the nucleotide sequences of parts of the major noncoding region of mitochondrial DNA (mtDNA) from the major geographic populations of humans. Dates of branchings in the mtDNA tree among humans were estimated with an improved maximum likelihood method. Two species of chimpanzees were used as an outgroup, and the mtDNA clock was calibrated by assuming that the chimpanzee/human split occurred 4 million years ago, following our earlier works. A model of homogeneous evolution among sites does not fit well with the data even within hypervariable segments, and hence an additional parameter that represents a proportion of variable sites was introduced. Taking account of this heterogeneity among sites, the date for the deepest root of the mtDNA tree among humans was estimated to be 280,000±50,000 years old (±1 SE), although there remains uncertainty about the constancy of the evolutionary rate among lineages. The evolutionary rate of the most rapidly evolving sites in mtDNA was estimated to be more than 100 times greater than that of a nuclear pseudogene.
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  • 6
    ISSN: 1432-1432
    Keywords: Hominoid mitochondrial DNA ; Nucleotide substitution rate ; Transition bias ; Base compositions ; Functional constraints ; Multiple hit corrections ; Transfer RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Focusing on the synonymous substitution rate, we carried out detailed sequence analyses of hominoid mitochondrial (mt) DNAs of ca. 5-kb length. Owing to the outnumbered transitions and strong biases in the base compositions, synonymous substitutions in mtDNA reach rapidly a rather low saturation level. The extent of the compositional biases differs from gene to gene. Such changes in base compositions, even if small, can bring about considerable variation in observed synonymous differences and may result in the region-dependent estimate of the synonymous substitution rate. We demonstrate that such a region dependency is due to a failure to take proper account of heterogeneous compositional biases from gene to gene but that the actual synonymous substitution rate is rather uniform. The synonymous substitution rate thus estimated is 2.37 ± 0.11 × 10−8 per site per year and comparable to the overall rate for the noncoding region. On the other hand, the rate of nonsynonymous substitutions differs considerably from gene to gene, as expected under the neutral theory of molecular evolution. The lowest rate is 0.8 × 10−9 per site per year forCOI and the highest rate is 4.5 × 10−9 forATPase 8, the degree of functional constraints (measured by the ratio of the nonsynonymous to the synonymous substitution rate) being 0.03 and 0.19, respectively. Transfer RNA (tRNA) genes also show variability in the base contents and thus in the nucleotide differences. The average rate for 11 tRNAs contained in the 5-kb region is 3.9 × 10−9 per site per year. The nucleotide substitutions in the genome suggest that the transition rate is about 17 times faster than the transversion rate.
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  • 7
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Human alloimmune cytotoxic T cells, sensitized selectively against the HLA-A2 antigen, were tested on a panel of selected target cells. Five HLA-A2 positive outlier cells could be identified. These outlier cells were only weakly lysed by HLA-A2 specific CTLs, although they were serologically indistinguishable from the other HLA-A2 positive, strongly lysed target cells. Furthermore, it was found that the outlier cells were poor cold target inhibitors in contrast to the other HLA-A2 positive target cells, which showed adequate inhibition of specific lysis of HLA-A2 positive target cells. Population studies indicate that the frequency of such HLA-A2 outlier cells may be approximately 10%.
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  • 8
  • 9
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The worldwide geographic and ethnic clustering of patients with diseases related to human T-cell lymphotropic virus type I (HTLV-I) may be explained by the natural history of HTLV-I infection. The genetic characteristics of indigenous people in the Andes are similar to those of the Japanese, ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 348 (1990), S. 651-653 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FIG. 1 Direct sequencing of the flanking region of nucleotide pair (np) 3,243 in a MELAS patient and a control. Nucleotide A in wild type is converted to a G at position 3,243. Because 22 tRNA genes are clustered in 11 locations, we synthesized 11 sets of 20-mer oligonucleotides with PCR-MATE ...
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