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  • Springer  (315)
  • EDP Sciences
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  • 1
    Digitale Medien
    Digitale Medien
    Man's place in hominoidea revealed by mitochondrial DNA genealogy (1992)
    Springer
    Journal of molecular evolution 35 (1992), S. 32-43 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Hominoid phylogeny ; Mitochondrial DNA ; Nucleotide substitutions ; Molecular clock ; Phylogenetic trees ; Divergence times
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00160258
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  • 2
    Digitale Medien
    Digitale Medien
    Evolution of hominoid mitochondrial DNA with special reference to the silent substitution rate over the genome (1993)
    Springer
    Journal of molecular evolution 36 (1993), S. 517-531 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Hominoid mitochondrial DNA ; Nucleotide substitution rate ; Transition bias ; Base compositions ; Functional constraints ; Multiple hit corrections ; Transfer RNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00556356
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  • 3
    Digitale Medien
    Digitale Medien
    Evolutionary relationship ofHLA-DRB genes inferred from intron sequences (1996)
    Springer
    Journal of molecular evolution 42 (1996), S. 648-657 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Major histocompatibility complex (Mhc) ; HumanMhc (HLA) ; DRB genes ; Gene duplication ; phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The major histocompatibility complex (Mhc) consists of class I and class II genes. In the humanMhc (HLA) class II genes, nineDRB loci have been identified. To elucidate the origin of these duplicated loci and allelic divergences at the most polymorphicDRBI locus, introns 4 and 5 as well as the 3′ untranslated region (altogether approximately 1,000 base pairs) of sevenHLA-DRB loci, threeHLA-DRBI alleles, and nine nonhuman primateDRB genes were examined. It is shown that there were two major diversification events inHLA-DRB genes, each involving gene duplications and allelic divergences. Approximately 50 million years (my) ago,DRBI *04 and an ancestor of theDRB1 *03 cluster (DRBI *03, DRBI*15, andDRB3) diverged from each other andDRB5, DRB7, DRB8, and an ancestor of theDRB2 cluster (DRB2, DRB4, andDRB6) arose by gene duplication. Later, about 25 my ago,DRBI *15 diverged fromDRBI*03, andDRB3 was duplicated fromDRBI *03. Then, some 20 my ago, the lineage leading to theDRB2 cluster produced two new loci,DRB4 andDRB6. TheDRBI *03 andDRBI *04 allelic lineages are extraordinarily old and have persisted longer than some duplicated genes. The orthologous relationships ofDRB genes between human and Old World monkeys are apparent, but those between Catarrhini and New World monkeys are equivocal because of a rather rapid expansion and contraction of primateDRB genes by duplication and deletion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02338798
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  • 4
    Digitale Medien
    Digitale Medien
    Evolution of Mhc–DRB Introns: Implications for the Origin of Primates (1999)
    Springer
    Journal of molecular evolution 48 (1999), S. 663-674 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Key words: Major histocompatibility complex (Mhc) — Intron evolution — Primate origin — Mammalian evolution — Scandentia — Chiroptera —DRB genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract. Introns are generally believed to evolve too rapidly and too erratically to be of much use in phylogenetic reconstructions. Few phylogenetically informative intron sequences are available, however, to ascertain the validity of this supposition. In the present study the supposition was tested on the example of the mammalian class II major histocompatibility complex (Mhc) genes of the DRB family. Since the Mhc genes evolve under balancing selection and are believed to recombine or rearrange frequently, the evolution of their introns could be expected to be particularly rapid and subject to scrambling. Sequences of intron 4 and 5 DRB genes were obtained from polymerase chain reaction-amplified fragments of genomic DNA from representatives of six eutherian orders—Primates, Scandentia, Chiroptera, Dermoptera, Lagomorpha, and Insectivora. Although short stretches of the introns have indeed proved to be unalignable, the bulk of the intron sequences from all six orders, spanning 〉85 million years (my) of evolution, could be aligned and used in a study of the tempo and mode of intron evolution. The analysis has revealed the Mhc introns to evolve at a rate similar to that of other genes and of synonymous sites of non-Mhc genes. No evidence of homogenization or large-scale scrambling of the intron sequences could be found. The Mhc introns apparently evolve largely by point mutations and insertions/deletions. The phylogenetic signals contained in the intron sequences could be used to identify Scandentia as the sister group of Primates, to support the existence of the Archonta superorder, and to confirm the monophyly of the Chiroptera.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00006510
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  • 5
    Digitale Medien
    Digitale Medien
    Multiplication of 28S rDNA and NOR activity in chromosome evolution among ants of the Myrmecia pilosula species complex (1994)
    Springer
    Chromosoma 103 (1994), S. 171-178 
    Details
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Chromosomal localization of rDNA in samples of five taxa of the Myrmecia pilosula species complex (Hymeoptera: Formicidae: Myrmeciinae) with 2n=3 (M. croslandi), 8 (M. imaii), 10 (M. banksi), 18 (M. haskinsorum), and 27 (M. pilosula) was carried out by fluorescence in situ hybridization (FISH) using cloned M. croslandi rDNA (pMc.r2) including the coding region for 28S rRNA. Results show that (1) the 28S rDNA in the genome of these ants is repetitive and is localized in pericentromeric C-bands, (2) the number of chromosomes carrying rDNA is two in M. croslandi, M. imaii and M. banksi, six in M. haskinsorum and ten in M. pilosula, and (3) only one or two clusters of rRNA genes generate nucleoli in each species. We suggest that the rDNA in the ancestral stock of the M. pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission. Most rDNA multiplied on various chromosomes seems to be inactivated and eliminated from the genome, together with C-bands, by $${\text{A}}\overline {\text{M}} $$ -inversion or centric fusion, with the remnant rDNAs dispersed in the genome by centric fission and $${\text{A}}\overline {\text{M}} $$ -inversion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368009
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  • 6
    Digitale Medien
    Digitale Medien
    Multiplication of 28S rDNA and NOR activity in chromosome evolution among ants of the Myrmecia pilosula species complex (1994)
    Springer
    Chromosoma 103 (1994), S. 171-178 
    Details
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Chromosomal localization of rDNA in samples of five taxa of the Myrmecia pilosula species complex (Hymenoptera: Formicidae: Myrmeciinae) with 2n=3 (M. croslandi), 8 (M. imaii), 10 (M. banksi), 18 (M. haskinsorum), and 27 (M. pilosula) was carried out by fluorescence in situ hybridization (FISH) using cloned M. croslandi rDNA (pMc.r2) including the coding region for 28S rRNA. Results show that (1) the 28S rDNA in the genome of these ants is repetitive and is localized in pericentromeric C-bands, (2) the number of chromosomes carrying rDNA is two in M. croslandi, M. imaii and M. banksi, six in M. haskinsorum and ten in M. pilosula, and (3) only one or two clusters of rRNA genes generate nucleoli in each species. We suggest that the rDNA in the ancestral stock of the M. pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission. Most rDNA multiplied on various chromosomes seems to be inactivated and eliminated from the genome, together with C-bands, by AM¯-inversion or centric fusion, with the remnant rDNAs dispersed in the genome by centric fission and AM¯-inversion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368009
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  • 7
    Digitale Medien
    Digitale Medien
    Polymorphism of the HLA class II loci in Siberian populations (1998)
    Springer
    Human genetics 〈Berlin〉 102 (1998), S. 27-43 
    Details
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The populations that colonized Siberia diverged from one another in the Paleolithic and evolved in isolation until today. These populations are therefore a rich source of information about the conditions under which the initial divergence of modern humans occurred. In the present study we used the HLA system, first, to investigate the evolution of the human major histocompatibility complex (MHC) itself, and second, to reveal the relationships among Siberian populations. We determined allelic frequencies at five HLA class II loci (DRB1, DQA1, DQB1, DPA1, and DPB1) in seven Siberian populations (Ket, Evenk, Koryak, Chukchi, Nivkh, Udege, and Siberian Eskimo) by the combination of single-stranded conformational polymorphism and DNA sequencing analysis. We then used the gene frequency data to deduce the HLA class II haplotypes and their frequencies. Despite high polymorphism at four of the five loci, no new alleles could be detected. This finding is consistent with a conserved evolution of human class II MHC genes. We found a high number of HLA class II haplotypes in Siberian populations. More haplotypes have been found in Siberia than in any other population. Some of the haplotypes are shared with non-Siberian populations, but most of them are new, and some represent “forbidden” combinations of DQA1 and DQB1 alleles. We suggest that a set of “public” haplotypes was brought to Siberia with the colonizers but that most of the new haplotypes were generated in Siberia by recombination and are part of a haplotype pool that is turning over rapidly. The allelic frequencies at the DRB1 locus divide the Siberian populations into eastern and central Siberian branches; only the former shows a clear genealogical relationship to Amerinds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004390050650
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  • 8
    Digitale Medien
    Digitale Medien
    Highly efficient solubilization of natural lignocellulosic materials by a commercial cellulase immobilized on various solid supports (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 306-311 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A commercial preparation of cellulase was immobilized on CNBr-sepharose, ConA-sepharose, and CNBr-glass beads. When filter paper was used as the substrate, the specific activity of the enzyme immobilized on ConA-sepharose was more than twice that of the soluble enzyme, while the activity of the enzymes immobilized on the other two substrates was either very slightly (CNBr-sepharose) or slightly (CNBr-glass beads) reduced. The immobilized enzymes showed alterations both in the Km and V max values: these were generally either slightly increased (Km) or reduced (V max). In addition, the immobilized enzymes were more resistant to inhibition both by glucose and cellobiose, they were all more stable than the soluble enzyme and solubilized three different natural lignocellulosic materials (alfa-alfa, wheat straw, and pine needles) to a much greater or significantly greater extext than the soluble enzyme: the ConA-sepharose cellulase was the most efficient. The possibility of reusing the immobilized enzyme was also tested. It was found that the ConA-sepharose cellulase could be reused five times with a final loss of activity that ranged between 30% and 50%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00253776
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  • 9
    Digitale Medien
    Digitale Medien
    Water-mass influences on summer Antarctic phytoplankton biomass and community structure (1995)
    Springer
    Polar biology 15 (1995), S. 15-20 
    Details
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The association between the variability of phytoplankton biomass and community structure and the distribution of water masses around the Antarctic Peninsula were examined during austral summer 1993. Phytoplankton biomass showed high variability, and was dominated by an autotrophic flagellate (Cryptomonas sp.) that represented, on average, 91% of total phytoplankton biomass. The lowest phytoplankton biomasses were associated with the strongly mixed, saline, cold waters characteristic of the Weddell Sea water mass, and with the waters influenced by ice melt from the Bellingshausen Sea. The highest biomasses were found in the confluence of these water masses, where a front develops. Community composition also differed among water masses, with eukariotic picoplankton and diatoms having their highest relative contribution to community biomass in stations with Bellingshausen Sea and Weddell Sea water masses, whereas the abundance of Cryptomonas sp. was highest at the confluence of these waters. These results indicate that mesoscale processes, that determine water mass distribution, are of paramount importance in controlling the time and space variability of Antarctic phytoplankton.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00236119
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  • 10
    Digitale Medien
    Digitale Medien
    Some comments on calibration of molecular evolutionary rates (1992)
    Springer
    Immunogenetics 36 (1992), S. 126-129 
    Details
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215290
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