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  • Evolution  (188)
  • Adaptation
  • Springer  (225)
  • 1985-1989  (161)
  • 1975-1979  (64)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 109-120 
    ISSN: 1476-5535
    Keywords: Ground water ; Biodegradation ; Hydrocarbon ; Adaptation ; Subsurface ; Creosote ; Microorganism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The microbial ecology of pristine, slightly contaminated, and heavily contaminated subsurface materials, and four subsurface materials on the periphery of the plume at an abandoned creosote waste site was investigated. Except for the unsaturated zone of the heavily contaminated material, mineralization of glucose (13.5 ppb) indicated a metabolically active microflora in all subsurface materials. However, mineralization (〈40%) of naphthalene, phenanthrene, and 2-methylnaphthalene was observed in contaminated material and material from the periphery of the plume, but not in pristine material. Pentachlorophenol was mineralized in material from the periphery of the plume. Inorganic and organic nutrient amendments and changes in pH and temperature did not increase the extent of mineralization of the aromatic compounds. An array of organic compounds found in creosote were biotransformed in contaminated ground water; however some compounds were still detected after 7 months of incubation. The data suggest that the subsurface microflora in slightly and heavily contaminated subsurface materials and materials from the periphery of the plume has adapted to degrade many compounds found in creosote.
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  • 2
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    Acta biotheoretica 35 (1986), S. 77-106 
    ISSN: 1572-8358
    Keywords: Evolution ; nonequilibrium thermodynamics ; boundary conditions models ; initial conditions models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Proponents of two axioms of biological evolutionary theory have attempted to find justification by reference to nonequilibrium thermodynamics. One states that biological systems and their evolutionary diversification are physically improbable states and transitions, resulting from a selective process; the other asserts that there is an historically constrained inherent directionality in evolutionary dynamics, independent of natural selection, which exerts a self-organizing influence. The first, the Axiom of Improbability, is shown to be nonhistorical and thus, for a theory of change through time, acausal. Its perception of the improbability of living states is at least partially an artifact of closed system thinking. The second, the Axiom of Historically Determined Inherent Directionality, is supported evidentially and has an explicit historical component. Historically constrained dynamic populations are inherently nonequilibrium systems. It is argued that living, evolving systems, when considered to be historically constrained nonequilibrium systems, do not appear improbable at all. Thus, the two axioms are not compatible. Instead, the Axiom of Improbability is considered to result from an unjustified attempt to extend the contingent proximal actions of natural selection into the area of historical, causal explanations. It is thus denied axiomatic status, and the effects of natural selection are subsumed as an additional level of constraint in an evolutionary theory derived from the Axiom of Historically Determined Inherent Directionality.
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  • 3
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    Cellular and molecular life sciences 41 (1985), S. 1080-1082 
    ISSN: 1420-9071
    Keywords: Evolution ; evolutionary rate ; stasis ; brain ; encephalization ; body size ; fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Constant evolutionary rates are possible only in verylarge populations, where natural selection does not exhaust varition because mutation supplies fresh variability. In a small population where a small number of genes influence an integrated system like brain and body size which have an allometric relationship, variation is removed rapidly under natural selection, This occurs even when the final fitness of the population is not optimal.
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  • 4
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    Cellular and molecular life sciences 43 (1987), S. 202-205 
    ISSN: 1420-9071
    Keywords: Evolution ; substrate specificity ; serological homologies ; flavone biosynthesis ; Silene ; glycosyltransferases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The variation in flavone glycosylation patterns inSilene is the result of the expression of six genetic loci, which control either the presence of allozymes differing in substrate specificity or isozymes regulated differently during development. Serological studies showed that at least three of these six loci are evolutionarily related. The genetic mechanisms leading to these complicated variation patterns and the role of this polymorphism for the plant in its interaction with the environment are discussed.
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  • 5
    ISSN: 1432-0983
    Keywords: psbA ; Cyanelle ; Cyanophora paradoxa ; Evolution ; Sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The psbA gene is part of the reaction center of photosystem II in cyanobacteria and the plastids of higher plants. Its primary sequence is highly conserved among all species investigated so far and its sequence shows homologies with the L and M subunits of the reaction center of photosynthetic bacteria. We have analyzed the psbA homolog from a eukaryotic alga, Cyanophora paradoxa, where the gene is encoded on cyanelle DNA. These cyanelles are surrounded by a murein sacculus and resemble cyanobacteria in many other characteristics, although they are genuine organelles that functionally replace plastids. Analysis of the gene revealed a psbA protein identical in length (360 codons) with the cyanobacterial counterpart. The overall sequence identity is, however, more pronounced between cyanelle psbA and the shorter (353 amino acids) psbA product found in higher plants. These data strongly support the postulated bridge position of cyanelles between chloroplasts and free-living cyanobacteria.
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  • 6
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    Current genetics 10 (1986), S. 931-941 
    ISSN: 1432-0983
    Keywords: T. aestivum ; Chloroplast DNA ; Repeat DNA ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Low-stringency hybridisation between recombinant plasmids representing the complete T. aestivum chloroplast genome has revealed small repeated DNA segments dispersed through the molecule. Thirty-two repeated DNA segments were detected, and they could be divided into 12 unrelated sets; no repeat was detected as multiple copies. The longest of the small repeats mapped just within the large inverted repeat in spinach and mung-bean ctDNAs. It was found to have been duplicated after the divergence of a cereal progenitor to generate a third, dispensible copy, 0.2 kbp downstream of rbcL. In maize at least, this copy has also become integrated, with rbcL, in the mitochondrial genome. Another of the repeats is thought to have mediated a chloroplast DNA inversion (Howe 1985). Thus the diverse collection of small repeats probably represents some consequences and causes of past recombination events as well as a mechanism for further intramolecular ctDNA recombination. Their possible significance in the restructuring and evolution of chloroplast genomes is discussed.
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  • 7
    ISSN: 1432-0983
    Keywords: Wheat chloroplast DNA ; Repeated sequences ; Ribosomal protein genes ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Some dispersed repeated sequences and their flanking regions from wheat and maize ctDNAs have been characterized. Two sets of wheat ctDNA repeats were found to be the chloroplast ribosomal protein genesrpl2 andrpl23, plus nonfunctional segments of them, designatedrpl2′ andrpl23′. Pairwise comparisons were made between the wheatrp123 andrpl23′, and the maizerp123′ sequences. The precise patterns of homology suggest that the divergence of the wheat and maize nonfunctional (rpl23′) sequences is being retarded by nonreciprocal recombination, biased by selection for individuals with functional (rpl23) sequences. The implied involvement of these sequences in mechanisms of homologous recombination, and therefore in the creation and spread of new ctDNA variants, is discussed.
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  • 8
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    Current genetics 15 (1989), S. 99-106 
    ISSN: 1432-0983
    Keywords: Yeast ; Isoleucyl-tRNA synthetase ; Isoleucine ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The isoleucyl-tRNA synthetase gene (ILS1) from the yeast Saccharomyces cerevisiae was cloned and sequenced. This gene was initially cloned because it cross-hybridizated to what is now presumed to be the isoleucyl-tRNA synthetase gene (cupC) from the protozoan Tetrahymena hhermophila. The ILS1 gene was determined to be 1,072 amino acids in length. A comparison with a recently published sequence of ILS1 1 from another laboratory (Englisch et al. 1987) was made and differences noted. Two promoter elements were detected, one for general amino acid control and one for constitutive transcription. A heat shock protein (hsp70) gene (probably SSA3) was found 237 by upstream from the ILS1 translation start site. The ILS1 amino acid sequence was compared to isoleucyl-tRNA synthetases from other organisms, as well as to valyl-, leucyl- and methionyl-tRNA synthetases. Regions of conservation between these enzymes were found.
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  • 9
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    Current genetics 15 (1989), S. 221-229 
    ISSN: 1432-0983
    Keywords: Chloroplast DNA ; Chlorophyll a/c alga ; Evolution ; Ribosomal operon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary There are almost no data describing chloroplast genome organization in chromophytic (chlorophyll a/c) plants. In this study chloroplast ribosomal operon placement and gene organization has been determined for the golden-brown alga Olisthodiscus luteus. Ribosomal RNA genes are located on the chloroplast DNA inverted repeat structure. Nucleotide sequence analysis, demonstrated that in contrast to the larger spacer regions in land plants, the 16S–23S rDNA spacer of O. luteus is only 265 by in length. This spacer contains tRNAIle and tRNAAla genes which lack introns and are separated by only 3 bp. The sequences of the tRNA genes and 16S and 23S rDNA termini flanking the spacer were examined to determine homology between O. luteus, chlorophytic plant chloroplast DNA, and prokaryotes.
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  • 10
    ISSN: 1432-0983
    Keywords: Comparative restriction site mapping ; Gene mapping ; Deletions and additions ; Chloroplast genome ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The chloroplast genomes from the interfertile green algae Chlamydomonas eugametos and C. moewusii have been compared in their overall sequence organization. Physical mapping of Aval, BstEII and EcoRI restriction sites on the C. moewusii chloroplast genome revealed that this 292 kilobase-pair (kbp) genome is 49 kbp larger than the C. eugametos genome. Heterologous fragment hybridizations indicated the same order of common sequence elements on the two algal genomes. Almost all of the 49 kbp size difference is accounted for by the presence of two large extra sequences in C. moewusii: a 21 kbp sequence in the inverted repeat and a 5.8 kbp sequence in the single copy-region bordering the 16S ribosomal RNA (rRNA) genes. In addition to these two major deletion/addition differences, 42 restriction site and fragment length differences (ranging from 100 to 500 base pairs) were mapped on the two algal genomes. Surprisingly, the greatest density of these differences was found to be confined within the inverted repeat, one of the most conserved regions of land plant chloroplast genomes.
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  • 11
    ISSN: 1432-0983
    Keywords: Physarum polycephalum ; rRNA ; Sequence ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of the Physarum polycephalum small subunit ribosomal RNA (SSU rRNA) gene has been determined. Sequence data indicate that the mature 19S SSU rRNA is 1,964 nucleotides long. A complete secondary structure model for P. polycephalum SSU rRNA has been constructed on the basis of the Escherichia coli 16S rRNA model and data from comparative analyses of 28 different eukaryotic sequences. A “four-helix” model is presented for the central domain variable region. This model can be applied both to vertebrate and most lower eukaryotic SSU rRNAs. The increased size of P. polycephalum SSU rRNA relative to the smaller SSU rRNAs from such other lower eukaryotes, as Dictyostelium, Tetrahymena or Saccharomyces is due mainly to three G+C-rich insertions found in two regions known to be of variable length in eukaryotes. In a phylogenetic tree constructed from pairwise comparisons of eukaryotic SSU rRNA sequences, the acellular myxomycete P. polycephalum is seen to diverge before the appearance of the cellular mycomycete Dictyostelium discoideum.
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  • 12
    ISSN: 1432-0983
    Keywords: Evolution ; Sequence comparison ; RUBISCO ; Transit peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have isolated and characterized a full-length cDNA clone encoding the precursor of the small subunit (pSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO) from the green alga, Chlamydomonas moewusii. Comparison with the C. reinhardtii rbcS1 gene sequence reveals that both small subunit (SS) coding regions are 75% homologous and that their predicted mature polypeptide chains are each composed of 140 amino acids. In contrast, their transit peptides appear to be divergent. We also show that transcription of the C. moewusii rbcS gene(s) which generates a 1,230 and a 930 base mRNA species are light-stimulated/or accumulated during the light period of the cell cycle. Finally, the SS polypeptide sequences of fifteen different photosynthetic organisms are compared; this analysis reveals at least five well-conserved polypeptide domains.
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  • 13
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    Journal of molecular evolution 5 (1975), S. 187-197 
    ISSN: 1432-1432
    Keywords: Evolution ; Cytochrome C ; Substitution ; Covarion ; Monte-Carlo Simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A statistical analysis aimed at obtaining some informations on a possible correlation between simultaneous amino acid substitutions is proposed. This method is applied to a set of cytochromes C, at the level of tandem and triple substitutions separated along the peptide chain by 1 to 15 peptide bonds. Monte-Carlo simulations are performed and the results are compared. We find a significant occurence of three adjacent amino acid substitutions in which the first replacement requires a two nucleotide substitution. A possible explanation of this fact is proposed on the basis of covarions.
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  • 14
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    Journal of molecular evolution 7 (1976), S. 133-149 
    ISSN: 1432-1432
    Keywords: 5S rRNA ; Nucleotide Sequence Homology ; Evolution ; Mutation Frequencies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The problem of choosing an alignment of two or more nucleotide sequences is particularly difficult for nucleic acids, such as 5S ribosomal RNA, which do not code for protein and for which secondary structure is unknown. Given a set of ‘costs’ for the various types of replacement mutations and for base insertion or deletion, we present a dynamic programming algorithm which finds the optimal (least costly) alignment for a set of N sequences simultaneously, where each sequence is associated with one of the N tips of a given evolutionary tree. Concurrently, protosequences are constructed corresponding to the ancestral nodes of the tree. A version of this algorithm, modified to be computationally feasible, is implemented to align the sequences of 5S RNA from nine organisms. Complete sets of alignments and proto-sequence reconstructions are done for a large number of different con-figurations of mutation costs. Examination of the family of curves of total replacements inferred versus the ratio of transitions/trans-versions inferred, each curve corresponding to a given number of in-sertions-deletions inferred, provides a method for estimating relative costs and relative frequencies for these different types of mutation.
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  • 15
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    Journal of molecular evolution 5 (1975), S. 47-55 
    ISSN: 1432-1432
    Keywords: Gene Duplication ; Dipeptides ; Posterior Pituitary Peptide ; Evolution ; Protein Sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have compiled the dipeptide frequencies in 100 known protein sequences. We suggest that dipeptides which occur with low frequencies can be used to locate proteins where partial gene duplication may have taken place. The 48 residue sequence of posterior pituitary peptide contains two Cys Trp pairs. The adjacent portions of the sequence are compatible with a partial gene duplication in the evolutionary history of posterior pituitary peptide.
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  • 16
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    Journal of molecular evolution 6 (1975), S. 309-320 
    ISSN: 1432-1432
    Keywords: Aminoacyl Transfer ; Amino Acid Adenylate ; Imidazole Catalysis ; Evolution ; Peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly (U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly (U). At pH 7.1, transfer to poly (U) was five times as great as to poly (A) and transfer to a poly (A) poly (U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly (U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2′ hydroxyl groups throughout poly (U) and the 2′ (3) hydroxyl groups at the terminus of poly (U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
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  • 17
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    Journal of molecular evolution 7 (1976), S. 111-131 
    ISSN: 1432-1432
    Keywords: Crustacea ; Evolution ; Repeated DNA ; Molecular Hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Analysis of data obtained from molecular hybridization of3H-labeled repetitious DNA has been utilized to reconstruct the broad outlines of phylogenetic relationships among decapod Crustacea. This molecular reconstruction agrees reasonably well with the paleontological record, and with other schemes obtained by comparative morphological and serological approaches. Preliminary evidence is in line with the hypothesis that continuous addition of new repeated sequence families to the genome over long periods of time may in part account for the correlation observed between percent repetitious DNA hybridized and divergence time. It is tentatively concluded that a core of DNA base sequence homology has been highly conserved throughout the evolution of theCrustacea. Demonstration of inter-species sequence homology has important implications to models which relegate a genetic regulatory function to repeated DNAs.
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  • 18
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    Journal of molecular evolution 7 (1976), S. 185-195 
    ISSN: 1432-1432
    Keywords: Evolution ; Randomicity ; Counter-Example
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Specific counter-examples are derived theoretically to the hypothesis that a random amino acid composition signifies a random evolutionary process.
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  • 19
    ISSN: 1432-1432
    Keywords: Bacilli, 16S rRNA ; Phylogeny ; Thermophile ; Evolution ; Oligonucleotide Fingerprint
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two modifications in the Sanger two dimensional electrophoretic procedure for RNA analysis are reported. One increases resolution on the primary fingerprint to the point that digests of large RNAs, of the size 1500–3000 nucleotides yield well resolved fingerprint patterns. The other is a novel endonucleolytic procedure that proves useful in determining sequences of the large oligonucleotides produced by T1 ribonuclease. These modifications have been used in determining the catalogs of oligomers produced by T1 ribonuclease digestion of 16S rRNAs from three related organisms,Bacillus subtilis, B.pumilus andB.stearothermophilus. The possible effects of adaptation to a thermophilic niche on ribosomal RNA primary structure and the phylogenetic relatedness of the two mesophilic Bacilli are discussed.
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  • 20
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    Journal of molecular evolution 6 (1975), S. 149-163 
    ISSN: 1432-1432
    Keywords: Electrophoretic Detectability ; Neutral Mutation Theory ; Evolution ; Mutation Rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Routine electrophoretic surveys for genetic variation in natural populations depend primarily upon detecting differences in the net charge carried by a protein. We have calculated the proportion of base substitutions which would yield an electrophoretically detectable mutant protein, and the relative mutation rates among different charge classes, under a variety of simplifying assumptions. These calculations indicate that: (i) only 25 per cent of all single base mutations would lead to a charge change on a protein molecule. (ii) five distinct classes of electrophoretic variants can be generated from a specified protein by single base substitutions. (iii) the relative mutation rates differ markedly among the different charge classes which can be generated by single base substitutions. The estimates of the proportion of electrophoretically detectable mutant proteins and relative mutation rates among charge classes were relatively robust to changes in assumptions concerned with the kind and site of base substitutions and the amino acid composition of the protein.
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  • 21
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    Journal of molecular evolution 8 (1976), S. 79-94 
    ISSN: 1432-1432
    Keywords: Histones ; Evolution ; Prokaryotes ; Lower Eukaryotes ; Higher Eukaryotes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence of basic chromosomal proteins in lower eukaryotes provides a useful approach to the study of histone evolution and function in higher eukaryotes. The histones of higher plants and animals are very similar and some are nearly identical, suggesting a high degree of evolutionary conservation within this group of proteins. However, a literature survey reveals that in the lower eukaryotes the histone situation is quite variable. The ciliates, and the true and cellular slime molds possess basic chromosomal proteins that are very similar to the histones of higher plants and animals. Various other lower eukaryotes possess basic chromosomal proteins that resemble at least some of the major histone fractions, and some microorganisms possess basic chromosomal proteins that bear little or no relationship to higher plant and animal histones. Since histones play a major role in the control of gene expression and the maintenance of chromosome structure in higher organisms, the evolution of these proteins represents a major change in the packaging of DNA and the mode of regulating gene expression in eukaryotes.
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  • 22
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    Journal of molecular evolution 8 (1976), S. 387-388 
    ISSN: 1432-1432
    Keywords: Nitrate Respiration ; Fermentation ; Energy Metabolism ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary E. Broda's recent argument against our concept that nitrate respiration antedated oxygen respiration is criticized.
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  • 23
    ISSN: 1432-1432
    Keywords: Evolution ; Repetitive DNA ; SI Nuclease ; Sequence Organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The organization of repetitive and single copy DNA sequences in sea urchin DNA has been examined with the single strand specific nuclease Sl fromAspergillus. Conditions and levels of enzyme were established so that single strand DNA was effectively digested while reassociated divergent repetitive duplexes remained enzyme resistant. About 25% of sea urchin DNA reassociates with repetitive kinetics to form Sl resistant duplexes of two distinct size classes derived from long and short repetitive sequences in the sea urchin genome. Fragments 2,000 nucleotides long were reassociated to Cot 20 and subjected to controlled digestion with Sl nuclease. About half of the resistant duplexes (13% of the DNA) are short, with a mode size of about 300 nucleotide pairs. This class exhibits significant sequence divergence, and principally consists of repetitive sequences which were interspersed with single copy sequences. About one-third of the long duplexes (4% of the DNA) are reduced in size after extensive Sl nuclease digestion to about 300 nucleotide pairs. About two-thirds of the long resistant duplexes (8% of the DNA) remains long after extensive SI nuclease digestion. These long reassociated duplexes are precisely base paired. The short duplexes are imprecisely paired with a melting temperature about 9°C below that of precisely paired duplexes of the same length. The relationship between length of repetitive duplex and precision of repetition is confirmed by an independent method and has been observed in the DNA of a number of species over a wide phylogenetic area.
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  • 24
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    Journal of molecular evolution 9 (1977), S. 131-158 
    ISSN: 1432-1432
    Keywords: Parvalbumins ; Evolution ; Maximum parsimony ; Troponin-C ; Myosin alkali light chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phylogenetic trees requiring the lowest sum of nucleotide replacements and gene duplicative events were constructed from the amino acid sequence data on ten gnathostome parvalbumins (PAR) and two related myofibrillar proteins troponin-C (TNC) and myosin alkali-light-chain (ALC). The origin and differentiation of the structural domains within these proteins were also investigated by the maximum parsimony method and by an alignment statistic for identifying evolutionarily related protein sequences. The results suggest, in agreement with the Weeds-McLachlan model, that tandem duplications in a precursor gene caused a primordial one-domain polypeptide (consisting of two helices with a calcium binding region in between) to double and then quadruple in size. Duplications of the gene coding for this four domain (I–II–III–IV) protein in an early metazoan, pre-gnathostome lineage gave rise to the separate loci for TNC, ALC, and PAR. TNC, which alone retained the Ca-binding function in each of its four domains, evolved much more slowly than either the ALC or PAR lineages. In the PAR lineage the I–II–III–IV structure was degraded, presumably by a partial gene deletion, to the II–III–IV structure during descent to the gnathostome ancestor of parvalbumins. Also during this period the mid region in domain II lost its Ca-binding function and, as it did so, evolved at an accelerated rate over other regions, a pattern indicative of positive selection for a change in function. In turn, from the gnathostome ancestor to the present, the mid regions of domains III and IV, which each retained Ca-bindung function, evolved much more slowly than other regions, a pattern indicative of stabilizing selection for preservation of function. Between the gnathostome and teleost-tetrapod ancestor a gene duplication separated the parvalbumins into anα-lineage and aβ-lineage. During this early vertebrate period PAR genes evolved at the extremely fast rate of 89 nucleotide replacements per 100 codons per 108 years (i.e. 89 NR %), but from the teleost-tetrapod ancestor to the present, bothα- andβ-PAR lineages evolved at a much slower rate, about 8 NR %. The use ofβ-parvalbumins as phylogenetic markers was complicated by presumptive evidence that paralogous (i.e. duplication dependent) gene lineages occur within this group. As a final point, in the genealogy of TNC, ALC, and PAR lineages, a non-random pattern of nucleotide replacements was observed between the reconstructed ancestral and descendant mRNA sequences. The pattern was similar to that observed for other protein genealogies and seems to reflect a bias in the genetic code for guanine to adenine and adenine to guanine transitions (especially at the first nucleotide position of the RNA codons) to produce amino acid substitutions which are compatible with the preservation of protein three-dimensional structure.
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  • 25
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    Journal of molecular evolution 6 (1975), S. 61-76 
    ISSN: 1432-1432
    Keywords: 5S ribosomal RNA ; Translation ; Evolution ; Molecular Architecture ; Conformational Changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An extensive comparative analysis of the available primary sequence data on 5S rRNA has been made. A universal secondary structure is presented for procaryotic 5S rRNA which contains four helical regions. Eucaryotic 5S rRNAs are found to have only three of these helices and thus have a somewhat different architecture. In addition, a highly conserved segment of more than thirty nucleotides is identified in the 5′ half of the procaryotic molecule. This segment includes the oligonucleotide-CGAAC- which presumably binds to the t-RNA “common” sequence-GTΨCG-. Among the eucaryotes, the plants display a procaryotic nature in this region, but no eucaryote has the sequence -CGAAC- in this segment. A functional role for the procaryotic 5S rRNA molecule is discussed in which it is envisioned to undergo conformational change, i.e., coiling and uncoiling of one of the helices, which can result in a cyclic interaction of the 5S rRNA molecule with two t-RNA molecules. A general principle also emerges: the natural rotational motion inherent in coiling and uncoiling of nucleic acid helices can be converted quite simply to linear mechanical motion.
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  • 26
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    Journal of molecular evolution 5 (1975), S. 279-290 
    ISSN: 1432-1432
    Keywords: E.coli ; Mutagenesis ; Evolution ; Gene Transposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The lactose fermenting genes inE.coli have been transposed to various chromosomal locations. The bacterial strains were mutagenized with different chemical mutagens and the frequency of Lac negative mutant colonies was measured as a function of lactose gene location in the chromosome. There appears to be a highly mutable location between 58–60 minutes on theE.coli map. This region does not appear to be correlated with the origin of DNA replication or with the terminus. The possible significance of this mutable region in the evolution of new bacterial genes is discussed.
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  • 27
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    Journal of molecular evolution 8 (1976), S. 143-153 
    ISSN: 1432-1432
    Keywords: 5S rRNA ; Comparative Analysis ; Secondary Structure ; Evolution ; Tuned Helix
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    Topics: Biology
    Notes: Summary The available comparative data on procaryotic 5S rRNA was extended through sequencing studies of eight gram positive procaryotes. Complete nucleotide sequences were presented for 5S rRNA fromBacillus subtilis, B. firmus, B.pasteurii, B.brevis, Lactobacillus brevis andStreptococcus faecalis. In addition, 5S rRNA oligonucleotide catalogs and partial sequence data were provided forB.cereus andSporosarcina ureae. These sequences and catalogs were discussed in terms of known features of procaryotic 5S rRNA architecture.
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    Journal of molecular evolution 9 (1976), S. 25-35 
    ISSN: 1432-1432
    Keywords: Genome organization ; Evolution ; Mitochondria
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    Notes: Summary The mitochondrial genome of yeast (S. cerevisiae orS. carlsbergensis) appears to be formed by 60–70 genetic units, each one of which is formed by (1) a GC-rich sequence, possibly having a regulatory role; (2) a gene, and (3) an AT-rich spacer, which probably is not transcribed. Recombination in this genome appears to underlie a number of important phenomena. The organization of the mitochondrial genome of yeast and these recombinational events are discussed in relationship with the organization and evolution of the nuclear genome of eukaryotes.
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  • 29
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    Journal of molecular evolution 9 (1977), S. 343-347 
    ISSN: 1432-1432
    Keywords: Evolution ; Haemoglobin ; Cooperativity ; Lamprey ; Maximum parsimony
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    Notes: Summary The sequences ofPetromyzon andAplysia globins are compared with the postulated vertebrate and mollusc-vertebrate ancestors to see if differences exist in the rates of evolution of different types of residue positions. Between the mollusc-vertebrate ancestor andAplysia globin there is no very striking pattern of changes except that the interior positions are relatively conserved. In the evolution ofPetromyzon haemoglobin, theα 1 β 2 contact area is relatively conserved. The homopolymeric binding of lamprey Hb seems to be a primitive function.
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  • 30
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    Journal of molecular evolution 9 (1977), S. 369-371 
    ISSN: 1432-1432
    Keywords: Methanogenic bacteria ; Primitive atmosphere ; Evolution ; Ecology ; Methane-carbon dioxide cycle
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    Topics: Biology
    Notes: Summary The phenotype and antiquity of methanogenic bacteria suggest them to have been one of the major factors determining a dynamic balance between CO2 and CH4 in the primitive atmosphere.
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    Journal of molecular evolution 25 (1987), S. 141-150 
    ISSN: 1432-1432
    Keywords: 20S particle ; Prosome ; Evolution ; Small cytoplasmic RNAs ; Heat shock proteins
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    Topics: Biology
    Notes: Summary We have purified and characterized a particle sedimenting at 20S from the postribosomal fraction of yeast, wheat germ,Drosophila melanogaster tissue culture cells, chicken embryo fibroblasts, rabbit reticulocyte lysate, and HeLa cells. Most of the protein constituents of the 20S particle have molecular weights of 20–35 kd and differ between species; however, some do have similar molecular weights and isoelectric points, suggesting they are related. Several low-molecular-weight RNAs, distinct from tRNAs, co-purify with the particle isolated from all these species and show increasingly more complex patterns ascending the arbitrary order from yeast to human (yeast, plant, insect, bird, and mammals). InDrosophila, we present evidence that these small RNAs are tightly associated with this 20S structure.
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  • 32
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    Journal of molecular evolution 28 (1988), S. 98-112 
    ISSN: 1432-1432
    Keywords: rRNA ; Evolution ; Sequence comparison ; Parsimony ; Bootstrap
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    Notes: Summary Sequences of small subunit (SSU) and large subunit (LSU) ribosomal RNA genes from archaebacteria, eubacteria, and the nucleus, chloroplasts, and mitochondria of eukaryotes have been compared in order to identify the most conservative positions. Aligned sets of these positions for both SSU and LSU rRNA have been used to generate tree diagrams relating the source organisms/organelles. Branching patterns were evaluated using the statistical bootstrapping technique. The resulting SSU and LSU trees are remarkably congruent and show a high degree of similarity with those based on alternative data sets and/or generated by different techniques. In addition to providing insights into the evolution of prokaryotic and eukaryotic (nuclear) lineages, the analysis reported here provides, for the first time, an extensive phylogeny of the mitochondrial lineage.
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  • 33
    ISSN: 1432-1432
    Keywords: Aspergillus nidulans ; 5S rRNA ; Pseudogenes ; Evolution
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    Notes: Summary AllAspergillus nidulans 5S rRNA pseudogenes known so far are the result of integration of an approx. 0.2-kbp-long DNA sequence into the 5S rRNA genes. This sequence, called block C, is present in at least five copies in theA. nidulans genome and seems to be associated either with 5S rRNA genes or pseudogenes. In contrast to the 78% sequence conservation of the C-block in pseudogenes, the truncated 5′ halves of the pseudogenes are very highly conserved (96.9–100%). We postulate that the 5S rRNA pseudogenes are still a subject of concerted evolution. The C-block sequence shows similarity to the switch region of the mouse heavy chain immunoglobulin gene. A characteristic motif GGGTGAG is repeated several times in both sequences; the sequence conservation is 63%.
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  • 34
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    Journal of molecular evolution 28 (1989), S. 175-184 
    ISSN: 1432-1432
    Keywords: Sheep ; Globin genes ; Evolution ; Gene duplication
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    Notes: Summary Domestic sheep have two common alleles at the adult β-globin locus,β A andβ B. Here we report the structure of the β-globin locus of A-haplotype sheep. The locus consists of 12 genes, organized as a triplicated 4-gene set: 5′ ∈I-∈II-ΨβI-βC-∈III-∈IV-ΨβII-βA-∈V-∈VI-ΨβIII-βF 3′. This arrangement is identical to that of the closely related goat locus. Sheep with the B haplotype have a locus arrangement consisting of a duplicated four-gene set, lacking the βC gene as well as three other genes present in A sheep and goats. In order to understand the evolutionary history of the B sheep locus, we have sequenced the βB gene from these sheep, and the βB gene from A-haplotype sheep, and compared the sequences to those of the sheep βA, goat βC, and βA, and cow adult β genes. Our results indicate that the βB gene has diverged recently from the βA gene, and therefore the βB locus structure may have resulted from a recent deletion from a triplicated locus.
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  • 35
    ISSN: 1432-1432
    Keywords: Evolution ; Multiple sequence alignment ; NTP binding ; Phylogenetic analysis ; Positive-strand RNA viruses
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    Notes: Summary NTP-motif, a consensus sequence previously shown to be characteristic of numerous NTP-utilizing enzymes, was identified in nonstructural proteins of several groups of positive-strand RNA viruses. These groups include picorna-, alpha-, and coronaviruses infecting animals and como-, poty-, tobamo-, tricorna-, hordei-, and furoviruses of plants, totalling 21 viruses. It has been demonstrated that the viral NTP-motif-containing proteins constitute three distinct families, the sequences within each family being similar to each other at a statistically highly significant level. A lower, but still valid similarity has also been revealed between the families. An overall alignment has been generated, which includes several highly conserved sequence stretches. The two most prominent of the latter contain the socalled “A” and “B” sites of the NTP-motif, with four of the five invariant amino acid residues observed within these sequences. These observations, taken together with the results of comparative analysis of the positions occupied by respective proteins (domains) in viral multidomain proteins, suggest that all the NTP-motif-containing proteins of positive-strand RNA viruses are homologous, constituting a highly diverged monophyletic group. In this group the “A” and “B” sites of the NTP-motif are the most conserved sequences and, by inference, should play the principal role in the functioning of the proteins. A hypothesis is proposed that all these proteins posses NTP-binding capacity and possibly NTPase activity, performing some NTP-dependent function in viral RNA replication. The importance of phylogenetic analysis for the assessment of the significance of the occurrence of the NTP-motif (and of sequence motifs of this sort in general) in proteins is emphasized.
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  • 36
    ISSN: 1432-1432
    Keywords: Ribosome ; 5S RNA ; Conformation ; Evolution
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    Notes: Summary Fox and Woese (1975a) have shown that a model of 5S RNA secondary structure similar to the one originally derived forChlorella 5S RNA can be generalized with relatively minor variations to all sequenced 5S RNA molecules, i.e. that corresponding base paired regions can be formed at approximately the same positions. We present experimental data in favour of this hypothesis and show that the points at which ribonucleases T1, T2 and pancreatic ribonuclease cleave six different 5S RNA molecules under ‘mild’ conditions (high ionic strength, low temperature, low RNAase concentration) nearly always fall in the proposed single-stranded regions. We conclude that this model is a good approximation to the conformation of 5S RNA in solution.
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  • 37
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    Journal of molecular evolution 10 (1977), S. 123-135 
    ISSN: 1432-1432
    Keywords: Ancestral sequence ; Eye lens protein ; Evolution ; Phylogenetic tree
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    Notes: Summary The sequences of the A chains of the eye lens proteinα-crystallin from seventeen mammalian species were compared. They showed a generally slow rate of evolution, but with marked variations in different lineages. Most substitutions have occurred in the C-terminal part of the chain, which probably forms part of the surface of theα-crystallin aggregate. The ancestral sequence method of Dayhoff revealed interesting indications about the phylogenetic relationships between the eleven mammalian orders that were represented by the investigated species. Most evident was the divergence of marsupial and placental orders. A notable resemblance between the hyrax and elephant sequences was observed, setting them apart from the ungulates, including whale. Primates, rodents, lagomorphs, insectivores and tupaiids seem to derive from a common stem group. These phylogenetic inferences are discussed in relation to current palaeontological and taxonomical opinions, and compared to evidence from other protein sequence data.
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  • 38
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    Journal of molecular evolution 11 (1978), S. 109-120 
    ISSN: 1432-1432
    Keywords: Origin of Life ; Genetic code ; Protein synthesis ; Evolution ; Prebiotic reactions
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    Notes: Summary The fact that proteins contain onlya-amino acids and that protein structure is determined by 3′ → 5′ linked ribonucleotides is postulated to be the result of the copolymerization of these molecules in the prebiotic environment. Ribonucleotides therefore represent partial degradation products and proteins represent a side reaction developing from copolymerization. The basic structural unit of copolymerization is a nucleotide substituted with an amino acid at the 2′ position. Characteristics of modern amino and ribonucleic acid structure are all consistent with and necessary for this hypothesis. The characteristics and individual base assignments of the code also provide strong support for origin from the postulated copolymers. All characteristics of the code can be accounted for by this single hypothesis.
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  • 39
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    Journal of molecular evolution 11 (1978), S. 225-231 
    ISSN: 1432-1432
    Keywords: Phylogenetic denseness ; Phylogenetic trees ; Topology ; Molecular reconstructions ; Evolution ; Paleogenetics
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    Notes: Summary The concept of phylogenetic denseness bears critically on the accuracy of evolutionary pathways inferred from experimentally sequenced proteins isolated from extant species. In this paper I develop an objective measure,ρ, of denseness to supplement previous intuitive concepts and which permits one to use this concept in comparing the quality of different evolutionary reconstructions. This measure is used to examine several published phylogenetic trees: insulin, a-hemoglobin,β-hemoglobin, myoglobin, cytochromec, and the parvalbumin family. The paper emphasizes 1) the importance of denseness in accurately estimating the number of nucleotide replacements which separate homologous sequences when this estimation is made by the method of parsimony, 2) the value of this concept in assessing the quality of those estimates, and 3) the use of this concept as a biologically practical heuristic method for identifying poorly studied regions in a phylogenetic tree, whether or not the tree was obtained by the parsimony method.
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  • 40
    ISSN: 1432-1432
    Keywords: Tropomyosin ; Differential splicing ; Evolution ; Isochore ; Codon usage ; Sequence convergence ; Functional constraints
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    Notes: Summary We have cloned and determined the nucleotide sequence of a complementary DNA (cDNA) encoded by a newly isolated human tropomyosin gene and expressed in liver. Using the leastsquare method of Fitch and Margoliash, we investigated the nucleotide divergences of this sequence and those published in the literature, which allowed us to clarify the classification and evolution of the tropomyosin genes expressed in vertebrates. Tropomyosin undergoes alternative splicing on three of its nine exons. Analysis of the exons not involved in differential splicing showed that the four human tropomyosin genes resulted from a duplication that probably occurred early, at the time of the amphibian radiation. The study of the sequences obtained from rat and chicken allowed a classification of these genes as one of the types identified for humans. The divergence of exons 6 and 9 indicates that functional pressure was exerted on these sequences, probably by an interaction with proteins in skeletal muscle and perhaps also in smooth muscle; such a constraint was not detected in the sequences obtained from nonmuscle cells. These results have led us to postulate the existence of a protein in smooth muscle that may be the counterpart of skeletal muscle troponin. We show that different kinds of functional pressure were exerted on a single gene, resulting in different evolutionary rates and different convergences in some regions of the same molecule. Codon usage analysis indicates that there is no strict relationship between tissue types (and hence the tRNA precursor pool) and codon usage. G+C content is characteristic of a gene and does not change significantly during evolution. These results are in good agreement with an isochore composition of the genome, and thus suggest a similar chromosomal environment in chicken, rat, and human.
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  • 41
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    Journal of molecular evolution 27 (1988), S. 291-297 
    ISSN: 1432-1432
    Keywords: P1 P2 protamines ; Evolution ; Regulatory sequence ; Primordial sequence ; Similarity ; Alignment
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    Notes: Summary With the recent availability of the primary structural data for the trout, bovine, and mouse protamine genes, a detailed comparison of their structures has been made. This has revealed extensive conservation of potentially biologically significant regions. An inverse correlation is apparent between gene copy number and the number of sequence-distinct protamines synthesized with the number of CP-box-like (CCYPCCC) putative transcription modulating sequences situated 5′ to these genes. A common nucleotide sequence 5′ to the CP-box-like putative transcription modulating sequence(s) at the end of a common region has been identified. It is postulated that this is the testis-specific protamine P1 transcription regulator sequence. Evidence based on sequence similarity is also provided for the existence of a primordial protamine gene and a scheme for the evolution of vertebrate protamine genes is proposed.
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  • 42
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    Journal of molecular evolution 13 (1979), S. 95-101 
    ISSN: 1432-1432
    Keywords: Oparin Ocean ; Origin of Life ; Evolution ; Runaway greenhouse ; Photosynthesis ; Methanogenesis
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    Notes: Summary The widely accepted Oparin thesis for the origin and early evolution of life seems sufficiently far from the true state of affairs as to be considered incorrect. It is proposed that life on earth actually arose in the planet's atmosphere, however an atmosphere very different from the present one. Because of an extremely warm surface, the early earth may have possessed no liquid surface water, its water being partitioned between a molten crust and a fairly dense atmosphere. Early preliving systems are taken to arise in the droplet phase in such an atmosphere. The early earth, which resembled Venus then and to some extent now, underwent a transition to its present condition largely as a result of the evolution of methanogenic metabolism.
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    Journal of molecular evolution 29 (1989), S. 28-39 
    ISSN: 1432-1432
    Keywords: Transposable elements ; Zea mays ; Evolution ; Inverted repeats
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    Notes: Summary The Robertson's Mutator stock of maize exhibits a high mutation rate due to the transposition of theMu family of transposable elements. All characterizedMu elements contain similar ≈200-bp terminal inverted repeats, yet the internal sequences of the elements may be completely unrelated. Non-Mutator stocks of maize have a 20–100-fold lower mutation rate relative to Mutator stocks, yet they contain multiple sequences that hybridize to theMu terminal inverted repeats. Most of these sequences do not cohybridize to internal regions of previously clonedMu elements. We have cloned two such sequences from the maize line B37, a non-Mutator inbred line. These sequences, termedMu4 andMu5, have an organization characteristic of transposable elements and possess ≈200-bpMu terminal inverted repeats that flank internal DNA, which is unrelated to other clonedMu elements.Mu4 andMu5 are both flanked by 9-bp direct repeats as has been observed for otherMu elements. However, we have no direct evidence that they have recently transposed because they have not been found in known genes. Although the internal regions ofMu4 andMu5 are not related by sequence similarity, both elements share an unusual structural feature: the terminal inverted repeats extend more than 100 bp internally fromMu-similar termini. The distribution of these elements in maize lines and related species suggests thatMu elements are an ancient component of the maize genome. Moreover, the structure of theMu termini and the fact thatMu termini are found flanking different internal sequences leads us to speculate thatMu termini once may have been capable of transposing as independent entities.
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  • 44
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    Journal of molecular evolution 10 (1977), S. 93-96 
    ISSN: 1432-1432
    Keywords: Evolution ; Endosymbiosis ; Mitochondrion ; Photosynthetic
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    Notes: Summary The possibility is put forth that the mitochondrion did not originate from an endosymbiosis, 1–2 billion years ago, involving an aerobic bacterium. Rather, it arose by endosymbiosis in a much early, anaerobic period, and was initially a photosynthetic organelle, analogous to the modern chloroplast. This suggestion arises from a reconsideration of the nature of endosymbiosis. It ex-plains the remarkable diversity in mitochondrial information storage and processing systems.
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  • 45
    ISSN: 1432-1432
    Keywords: Lysozyme ; Insect ; Lepidoptera ; Evolution ; Sequence
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    Notes: Summary Sequence studies of the N-terminal halves of the lysozymes isolated fromBombyx mori, Galleria mellonella andSpodoptera littoralis (Lepidoptera) allow us to classify these enzymes among the c (chicken) type lysozymes.
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  • 46
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    Journal of molecular evolution 14 (1979), S. 287-300 
    ISSN: 1432-1432
    Keywords: Phenylalanine tRNA ; Methionine initiator tRNA ; Evolution ; Mutations ; Conformation
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    Notes: Summary Sequence data from methionine initiator and phenylalanine transfer RNAs were used to construct phylogenetic trees by the maximum parsimony method. Although eukaryotes, prokaryotes and chloroplasts appear related to a common ancestor, no firm conclusion can be drawn at this time about mitochondrial-coded transfer RNAs. tRNA evolution is not appropriately described by random hit models, since the various regions of the molecule differ sharply in their mutational fixation rates. ‘Hot’ mutational spots are identified in the TψC, the amino acceptor and the upper anticodon stems; the D arm and the loop areas on the other hand are highly conserved. Crucial tertiary interactions are thus essentially preserved while most of the double helical domain undergoes base pair interchange. Transitions are about half as costly as transversions, suggesting that base pair interchanges proceed mostly through G-U and A -C intermediates. There is a preponderance of replacements starting from G and C but this bias appears to follow the high G + C content of the easily mutated base paired regions.
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  • 47
    ISSN: 1432-1432
    Keywords: Xenopus tropicalis ; Xenopus borealis ; Globin cDNAs ; Evolution
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    Notes: Summary Globin mRNAs ofXenopus borealis andXenopus tropicalis have been cloned and sequenced. The nucleotide and derived amino acid sequences were compared with each other and with already available data fromXenopus laevis. This analysis rendered clear evidence that the common ancestor ofX. laevis andX. borealis, but not ofX. tropicalis, had lost one amino acid of the β-globins prior to a genome duplication event that preceded the segregation of the former two species. Replacement-site substitutions were used to calculate a rough time scale of genome duplication and species segregation. The results suggest an ancient separation between theX. laevis and theX. tropicalis groups occurring approximately 110–120 million years ago. Analysis of the amino acid chains demonstrated various alterations. However, some functional domains, like heme-binding sites andα1β2 contact sites, were subject to a high degree of conservation, indicating the existence of functional constraints on them also in the genusXenopus.
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  • 48
    ISSN: 1432-1432
    Keywords: Symbiosis ; Plant mitochondria ; 5S RNA ; Evolution ; Purple bacteria
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    Notes: Summary The complete nucleotide sequences of 5S ribosomal RNAs fromRhodocyclus gelatinosa, Rhodobacter sphaeroides, andPseudomonas cepacia were determined. Comparisons of these 5S RNA sequences show that rather than being phylogenetically related to one another, the two photosynthetic bacterial 5S RNAs share more sequence and signature homology with the RNAs of two nonphotosynthetic strains.Rhodobacter sphaeroides is specifically related toParacoccus denitrificans andRc. gelatinosa is related toPs. cepacia.These results support earlier 16S ribosomal RNA studies and add two important groups to the 5S RNA data base. Unique 5S RNA structural features previously found inP. denitrificans are present also in the 5S RNA ofRb. sphaeroides; these provide the basis for subdivisional signatures. The immediate consequence of our obtaining these new sequences is that we are able to clarify the phylogenetic origins of the plant mitochondrion. In particular, we find a close phylogenetic relationship between the plant mitochondria and members of the alpha subdivision of the purple photosynthetic bacteria, namely,Rb. sphaeroides, P. denitrificans, andRhodospirillum rubrum.
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    Journal of molecular evolution 22 (1985), S. 91-94 
    ISSN: 1432-1432
    Keywords: Primitive atmosphere ; Self-organization ; Evolution ; Prebiological chemistry ; Primordial soup ; Oparin thesis
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    Topics: Biology
    Notes: Summary A recently proposed model for the origin of prebiotic progenitors of life in particles suspended in a primitive, specially organized atmosphere is considered critically. It is concluded that the physical and chemical framework of the new hypothesis conflicts with the conditions necessary for the evolution of the progenitors of life in the atmosphere of the early Earth. Therefore this model seems not to be a reasonable alternative to the Oparin thesis.
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  • 50
    ISSN: 1432-1432
    Keywords: Nucleotide sequence ; Evolution ; Methanogens ; Extreme halophiles ; Eubacteria ; Eukaryotes
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    Notes: Summary The sequence of the small-subunit rRNA from the thermoacidophilic archaebacteriumSulfolobus solfataricus has been determined and compared with its counterparts from halophilic and methanogenic archaebacteria, eukaryotes, and eubacteria. TheS. solfataricus sequence is specifically related to those of the other archaebacteria, to the exclusion of the eukaryotic and eubacterial sequences, when examined either by evolutionary distance matrix analyses or by the criterion of minimum change (maximum parsimony). The archaebacterial 16S rRNA sequences all conform to a common secondary structure, with theS. solfataricus structure containing a higher proportion of canonical base pairs and fewer helical irregularities than the rRNAs from the mesophilic archaebacteria.S. solfataricus is unusual in that its 16S rRNA-23S rRNA intergenic spacer lacks a tRNA gene.
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  • 51
    ISSN: 1432-1432
    Keywords: Actin-coding regions ; Sequence divergence ; Conversion ; Codon usage ; Evolution
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    Notes: Summary We have determined the sequences of three recombinant cDNAs complementary to different mouse actin mRNAs that contain more than 90% of the coding sequences and complete or partial 3′ untranslated regions (3′UTRs): pAM 91, complementary to the actin mRNA expressed in adult skeletal muscle (αsk actin); pAF 81, complementary to an actin mRNA that is accumulated in fetal skeletal muscle and is the major transcript in adult cardiac muscle (αc actin); and pAL 41, identified as complementary to a β nonmuscle actin mRNA on the basis of its 3′UTR sequence. As in other species, the protein sequences of these isoforms are highly (〉93%) conserved, but the three mRNAs show significant divergence (13.8–16.5%) at silent nucleotide positions in their coding regions. A nucleotide region located toward the 5′ end shows significantly less divergence (5.6–8.7%) among the three mouse actin mRNAs; a second region, near the 3′ end, also shows less divergence (6.9%), in this case between the mouse β and αsk actin mRNAs. We propose that recombinational events between actin sequences may have homogenized these regions. Such events distort the calculated evolutionary distances between sequences within a species. Codon usage in the three actin mRNAs is clearly different, and indicates that there is no strict relation between the tissue type, and hence the tRNA precursor pool, and codon usage in these and other muscle mRNAs examined. Analysis of codon usage in these coding sequences in different vertebrate species indicates two tendencies: increases in bias toward the use of G and C in the third codon position in paralogous comparisons (in the order αc), and in orthologous comparisons (in the order chicken 〈 rodent 〈 man). Comparison of actin-coding sequences between species was carried out using the Perler method of analysis. As one moves backward in time, changes at silent sites first accumulate rapidly, then begin to saturate after −(30–40) million years (MY), and actually decrease between −400 and −500 MY. Replacements or silent substitutions therefore cannot be used as evolutionary clocks for these sequences over long periods. Other phenomena, such as gene conversion or isochore compartmentalization, probably distort the estimated divergence time.
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    Journal of molecular evolution 5 (1975), S. 25-34 
    ISSN: 1432-1432
    Keywords: Rhodopseudomonas spheroides ; 16S Ribosomal RNA ; T1 Ribonuclease Digest ; Phylogeny ; Evolution
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    Topics: Biology
    Notes: Summary The 16S ribosomal RNA (30S subunit) ofRhodopseudomonas spheroides has been characterized in terms of T1 ribonuclease digestion products. This “fingerprint” ultimately permits the placement ofR. spheroides into a detailed procaryotic phylogenetic tree. Given the number of major procaryotic lines that have been characterized in these terms to date, one can tentatively place the Athiorhodaceae closer to the Vibrio-Enteric group than to the Bacillaceae or Cyanophyta.
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    Journal of molecular evolution 5 (1975), S. 35-46 
    ISSN: 1432-1432
    Keywords: Photobacter Strain 8265 ; 5S Ribosomal RNA ; Primary Structure ; Comparative Characterization ; Evolution ; Energetically Constrained Helix
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    Topics: Biology
    Notes: Summary Comparative sequencing studies provide powerful insights into molecular function and evolution. The sequence for 5S ribosomal RNA from Photobacter strain 8265 is eighteen base replacements removed from that ofEscherichia coli. Of these, the vast majority involve a G or C becoming an A or U. These variations also define unequivocally a hexanucleotide base paired region, which appears to be a universal feature of the 5S RNA molecule. The base composition of this helix seems to be under rather stringent, and so unusual, energetic constraints. The possible implications of this are discussed - in particular the prospect of a 5S RNA molecule that undergoes conformational transitions as a part of the overall state changes that constitute the function of the ribosome.
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  • 54
    ISSN: 1432-1432
    Keywords: 5S RNA ; Drosophila ; Evolution ; Secondary structure ; Development
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    Notes: Summary The nucleotide sequence ofDrosophila melanogaster 5S RNA has been determined and appears to be homogeneous both in the KC cell line and in the insect at different developmental stages. Experimental evidence on the conformation of this molecule is in agreement with a general class of 5S RNA models.
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    Journal of molecular evolution 9 (1977), S. 305-311 
    ISSN: 1432-1432
    Keywords: Comparative cataloging ; Methanogenic bacteria ; Phylogeny ; 16S ribosomal RNA ; Evolution
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    Notes: Summary The 16S ribosomal RNAs from two species of methanogenic bacteria, the mesophileMethanobacterium ruminantium and the thermophileMethanobacterium thermoautotropbicum, have been characterized in terms of the oligonucleotides produced by digestion withT 1 ribonuclease. These two organisms are found to be sufficiently related that they can be considered members of the same genus or family. However, they bear only slight resemblance to “typical” Procaryotic genera; such asEschericbia, Bacillus andAnacystis. The divergence of the methanogeinc bacteria from other bacteria may be the most ancient phylogenetic event yet detected — antedating considerably the divergence of the blue green algal line for example, from the main bacterial line.
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    Journal of molecular evolution 25 (1987), S. 248-254 
    ISSN: 1432-1432
    Keywords: Intervening sequence ; Evolution ; Archaebacteria
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    Notes: Summary Nucleotide sequences of four tRNA genes from the archaebacteriumSulfolobus solfataricus have been determined. Based upon DNA sequence analysis, three of the four genes contain presumptive intervening sequences (introns) in their anticodon loops. The three introns can form similar, but not identical, secondary structures. The cleavage site at the 3′ end of all three introns occurs in a three-base bulge loop. All four genes lack an encoded 3′ CCA terminus and are flanked by A+T-rich DNA sequences. Two of the genes are located on antiparallel DNA strands, with their 3′ termini separated by 414 bp of sequence. Including two previously published sequences, a total of five introns have now been detected among sixS. solfataricus tRNA genes. Occurrence of introns at corresponding locations in both archaebacterial and eukaryotic tRNA genes suggests that the intron/exon form of gene structure predates the evolutionary divergence of the archaebacteria and the eukaryotes.
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    Journal of molecular evolution 25 (1987), S. 261-269 
    ISSN: 1432-1432
    Keywords: Fimbriae ; Pili ; Protein structure ; Microbial phylogeny ; Evolution
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    Topics: Biology
    Notes: Summary We have analyzed and compared the amino acid sequences of the type 4 fimbrial subunits fromPseudomonas aeruginosa, Moraxella bovis, M. nonliquefaciens, Bacteroides nodosus, Neisseria gonorrhoeae, andN. meningitidis. We propose a consensus sequence for the highly conserved aminoterminal regions of these proteins. In the variable regions, a domain corresponding to an epitope common toN. gonorrhoeae andN. meningitidis fimbriae is conserved, both in sequence and in environment, in fimbrial subunits fromB. nodosus. The subunits fromM. bovis andP. aeruginosa do not show any homologies to this sequence. In all of the subunits, the carboxy-terminal half of the molecule consists of a series of fairly hydrophobic domains. The last three domains, two of which include the cysteines of the disulfide bridge inN. gonorrhoeae, P. aeruginosa, andM. bovis, are more or less conserved in sequence in all of the proteins including that ofB. nodosus. We propose that these conserved hydrophobic regions, which have the potential to form a series of beta-sheets, form a structural framework around which more variable hydrophilic sequences determining immunological profile are arranged. The evolutionary relationships of the contemporary proteins and the distribution of type 4 fimbriae are also discussed.
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    Journal of molecular evolution 26 (1987), S. 274-283 
    ISSN: 1432-1432
    Keywords: Cardiotoxin ; Circular dichroism ; Cytotoxin ; Evolution ; Protein
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    Notes: Summary In order to analyze the evolutionary behavior of the cobra venom cytotoxins, their probable tertiary structure was predicted using computer graphics. The 41 amino acid sequences known show that the major evolutionary changes have taken place in two particularly exposed areas of the molecular surface. In each area, neighboring residue positions seem to have evolved interdependently, but there is no obvious interdependence between the two areas. Indeed, the relative evolution of these two areas prompts a subdivision of the sequence set into four groups. According to the known cytotoxin circular dichroism spectra, one of these four groups could be characterized by a difference in molecular secondary structure. Sine the two variable areas have functional associations, it is suggested that their evolution may be governed by a target with several similar binding sites.
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    Journal of molecular evolution 26 (1987), S. 341-346 
    ISSN: 1432-1432
    Keywords: Evolution ; tRNA ; Recognition sites ; Statistics
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    Notes: Summary A compilation of known tRNA, and tRNA gene sequences from archaebacteria, eubacteria, and eukaryotes permits the construction of tRNA cloverleafs which show conserved structural elements for each tRNA family. Positions conserved across the three kingdoms are thought to represent archetypical features of tRNAs which preceded the divergence of these kingdoms.
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    Journal of molecular evolution 27 (1988), S. 17-28 
    ISSN: 1432-1432
    Keywords: Actin genes ; Evolution ; 5′ and 3′ untranslated regions
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    Notes: Summary We have sequenced the coding and leader regions, as well as part of the 3′ untranslated region, of aXenopus borealis type 1 cytoskeletal actin gene [defined according to the arrangement of acidic residues at the N-terminus; Vandekerckhove et al. (1981) J Mol Biol 152:413–426]. The encoded amino acid sequence is the same as the avian and mammalian β (type 1) cytoskeletal actins, except for an isoleucine at position 10 (as found in the mammalian γ cytoskeletal actins), and an extra amino acid, alanine, after the N-terminal methionine. Five introns were found, in the same positions as those of the rat and chicken β-actin genes. The 5′ and 3′ untranslated regions resemble those of the human γ (type 8) cytoskeletal actin gene more closely than the mammalian β genes. Primer extension showed that this type 1 gene is transcribed in ovary and tadpole. Sequencing of primer extension products demonstrated two additional mRNA species inX. borealis, encoding type 7 and 8 isoforms. This contrasts with the closely related speciesXenopus laevis, where type 4, 5, and 8 isoforms have been found. The type 7 isoform has not previously been found in any other species. The mRNAs of theX. borealis type 1 and 8 andX. laevis type 5 and 8 isoforms contain highly homologous leaders. TheX. borealis type 7 mRNA has no leader homology with the other mRNA species and, unlike them, has no extra N-terminal alanine codon. The evolutionary implications of these data are discussed.
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  • 61
    ISSN: 1432-1432
    Keywords: Histone genes ; Sea stars ; Echinoderms ; Evolution
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    Notes: Summary The arrangement of core histone genes and their transcriptional polarity has been determined for three species of sea stars (Pisaster ochraceus, P. brevispinus, andDermasterias imbricata) representing two orders which diverged over 500 million years ago. Each species has approximately 500 core histone cluster repeats per haploid genome. The close phylogenetic relationship between thePisaster species is evident from the correspondence of restriction sites in the repeat element, identical arrangement of core histones, and high degree of sequence homology in both the coding and spacer regions of the H3 gene. TheDermasterias repeat has the same gene order and transcriptional polarity of core histones, but its restriction map is significantly different. Moreover, theDermasterias H3 gene has the same amino acid sequence, but in comparison toPisaster nucleotide sequences, shows a high level of silent substitutions. Analyses of the nucleotide sequence of the 5′ and 3′ regions surrounding the H3 gene from each species demonstrate the presence of appropriately spaced consensus and processing signal segments. The 3′ spacer segment of theDermasterias H4 gene contains an unusual, threefold tandemly repeated, 21-nucleotide, AT-rich sequence. No similar sequence is seen in theP. brevispinus H4 3′ region, but these two species show a striking regularity of distribution of five different homologous oligomers in the 3′ spacer.
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    Journal of molecular evolution 27 (1988), S. 102-108 
    ISSN: 1432-1432
    Keywords: Hemopexin ; Evolution ; Gene structure ; Recombination ; Sequence homology
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    Notes: Summary The human hemopexin gene was isolated and its structure determined. The gene spans approximately 12 kb and is interrupted by nine introns. When the intron/exon pattern was examined with respect to the polypeptide segments they encode, a direct correspondence between exons and the 10 repeating units in the protein was observed. The introns are not randomly placed; they fall in the middle of the region of amino acid sequence homology in strikingly similar locations in 6 of the 10 units and in a symmetrical position in the two halves of the coding sequence. These features strongly support the hypothesis that the gene evolved through intron-mediated duplications of a primordial sequence to a five-exon cluster. A more recent gene duplication led to the present-day gene organization.
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    Journal of molecular evolution 14 (1979), S. 13-31 
    ISSN: 1432-1432
    Keywords: Mars ; Evolution ; Planetary geochemistry ; Soil ; Ionizing radiation ; Exobiology
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    Topics: Biology
    Notes: Summary Physical and chemical considerations permit the division of the near-surface regolith on Mars into at least six zones of distinct microenvironments. The zones are euphotic, duricrust/peds, tempofrost, permafrost, endolithic, and interfacial/transitional. Microenvironments vary significantly in temperature extremes, mean temperature, salt content, relative pressure of water vapor, UV and visible light irradiance, and exposure to ionizing radiation events (100 Mrad) and oxidative molecular species. From what is known of the chemistry of the atmossphere and regolith fines (soil), limits upon the aqueous chemistry of soil pastesmay be estimated. Heat of wetting could reach 45 cal/g dry soil; initial pH is indeterminate between 1 and 10; ionic strength and salinity are predicted to be extremely high; freezing point depression is inadequate to provide quantities of liquid water except in special cases. The prospects for biotic survival are grim by terrestrial standards, but the extremes of biological resiliency are inaccessible to evaluation. Second-generation in situ experiments which will better define Martian microenvironments are clearly possible. Antarctic dry valleys are approximations to Martian conditions, but deviate significantly by at least half-a-dozen criteria.
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    Journal of molecular evolution 29 (1989), S. 52-62 
    ISSN: 1432-1432
    Keywords: Genome organization ; Evolution ; Plant virus ; RNA recombination ; Sequence similarity
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    Notes: Summary The relationships of genome organization among elongated (rod-shaped and filamentous) plant viruses have been analyzed. Sequences in coding and noncoding regions of barley stripe mosaic virus (BSMV) RNAs 1, 2, and 3 were compared with those of the monopartite RNA genomes of potato virus X (PVX), white clover mosaic virus (WClMV), and tobacco mosaic virus, the bipartite genome of tobacco rattle virus (TRV), the quadripartite genome of beet necrotic yellow vein virus (BNYVV), and icosahedral tricornaviruses. These plant viruses belong to a supergroup having 5′-capped genomic RNAs. The results suggest that the genomic elements in each BSMV RNA are phylogenetically related to those of different plant RNA viruses. RNA 1 resembles the corresponding RNA 1 of tricornaviruses. The putative proteins encoded in BSMV RNA 2 are related to the products of BNYVV RNA 2, PVX RNA, and WClMV RNA. Amino acid sequence comparisons suggest that BSMV RNA 3 resembles TRV RNA 1. Also, it can be proposed that in the case of monopartite genomes, as a rule, every gene or block of genes retains phylogenetic relationships that are independent of adjacent genomic elements of the same RNA. Such differential evolution of individual elements of one and the same viral genome implies a prominent role for gene reassortment in the formation of viral genetic systems.
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  • 65
    ISSN: 1432-1432
    Keywords: Carcinoembryonic antigen ; Evolution ; Gene family ; Human ; Rat ; Synonymous substitutions ; Silent molecular clock ; Evolutionary trees
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    Notes: Summary Various rodent and primate DNAs exhibit a stronger intra- than interspecies cross-hybridization with probes derived from the N-terminal domain exons of human and rat carcinoembryonic antigen (CEA)-like genes. Southern analyses also reveal that the human and rat CEA gene families are of similar complexity. We counted at least 10 different genes per human haploid genome. In the rat, approximately seven to nine different N-terminal domain exons that presumably represent different genes appear to be present. We were able to assign the corresponding genomic restriction endonuclease fragments to already isolated CEA gene family members of both human and rat. Highly similar subgroups, as found within the human CEA gene family, seem to be absent from the rat genome. Hybridization with an intron probe from the human nonspecific cross-reacting antigen (NCA) gene and analysis of DNA sequence data indicate the conservation of noncoding regions among CEA-like genes within primates, implicating that whole gene units may have been duplicated. With the help of a computer program and by calculating the rate of synonymous substitutions, evolutionary trees have been derived. From this, we propose that an independent parallel evolution, leading to different CEA gene families, must have taken place in, at least, the primate and rodent orders.
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    Journal of molecular evolution 29 (1989), S. 180-187 
    ISSN: 1432-1432
    Keywords: Divergence ; Mitochondrial DNA ; Molecular evolution ; Constraints ; Two-parameter model ; Evolutionary distance ; Evolution ; Mutation ; Neutral space ; Variable positions
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    Notes: Summary Selective constraints on DNA sequence change were incorporated into a model of DNA divergence by restricting substitutions to a subset of nucleotide positions. A simple model showed that both mutation rate and the fraction of nucleotide positions free to vary are strong determinants of DNA divergence over time. When divergence between two species approaches the fraction of positions free to vary, standard methods that correct for multiple mutations yield severe underestimates of the number of substitutions per site. A modified method appropriate for use with DNA sequence, restriction site, or thermal renaturation data is derived taking this fraction into account. The model also showed that the ratio of divergence in two gene classes (e.g., nuclear and mitochondrial) may vary widely over time even if the ratio of mutation rates remains constant. DNA sequence divergence data are used increasingly to detect differences in rates of molecular evolution. Often, variation in divergence rate is assumed to represent variation in mutation rate. The present model suggests that differing divergence rates among comparisons (either among gene classes or taxa) should be interpreted cautiously. Differences in the fraction of nucleotide positions free to vary can serve as an important alternative hypothesis to explain differences in DNA divergence rates.
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    Journal of molecular evolution 29 (1989), S. 233-245 
    ISSN: 1432-1432
    Keywords: Mitochondrial DNA ; Salmonids ; Nucleotide sequence ; Transitions ; Transversions ; Evolution
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    Notes: Summary Sequence comparisons were made from 2214 bp of mitochondrial DNA cloned from six Pacific salmonid species. These sequences include the genes for ATPase subunit 6, cytochrome oxidase subunit 3, NADH dehydrogenase subunit 3, NADH dehydrogenase subunit 4L, tRNAGLY, and tRNAARG. Variation is found at 338 silent and 12 nonsilent positions of protein coding genes and 10 positions in the two tRNA sequences. A single 3-bp length difference was also detected. In all pairwise comparisons the sequence divergence observed in the fragment was higher than that previously predicted by restriction enzyme analysis of the entire molecule. The inferred evolutionary relationship of these species is consistent between methods. The distribution of silent variation shows a complex pattern with greatly reduced variation at the junctions of genes. The variation in the tRNA sequences is concentrated in the DHU loop. The close relationship of these species and extensive sequence analyzed allows for an analysis of the spectrum of substitutions that includes the frequencies of all 12 possible substitutions. The observed spectrum of substitutions is related to potential pathways of spontaneous substitution. The salmonid sequences show an extremely high ratio of silent to replacement substitutions. In addition the amino acid sequences of the four proteins coded in this fragment show a consistently high level of identity with theXenopus sequences. Taken together these data are consistent with a slower rate of amino acid substitution among the cold-blooded vertebrates when compared to mammals.
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  • 68
    ISSN: 1432-1432
    Keywords: α-Conotoxin ; α-Neurotoxin ; Erabutoxin b ; Evolution ; Venom
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    Topics: Biology
    Notes: Summary α-neurotoxins from elapid snake venoms andα-conotoxins from marine snails bind specifically and with high affinity to nicotinic cholinoceptors. Although both types of toxin are polypeptides, there is more than a fourfold difference in size between the two and no clear sequence homology is evident. A systematic computer search of the three-dimensional structure of erabutoxin b (anα-neurotoxin from the false sea snakeLaticauda semifasciata) was performed to identify the locality that most closely matched the amino acid compositions of the smallerα-conotoxins (from the marine snailsConus magus andConus geographus). The area of greatest similarity centered on residue position 25 of erabutoxin b, a locale that is conserved throughout the snakeα-neurotoxins and their homologues. Six Proteins unrelated to erabutoxin b were compared to theα-conotoxins to show that the extent of the erabutoxin b/α-conotoxin match was too high to be coincidental. Homologues of erabutoxin b, namelyα-cobratoxin fromNaja naja siamensis and cytotoxin VII4 fromNaja mossambica mossambica, were also analyzed. The extent of the matching with theα-conotoxins decreased in the series erabutoxin b〉α-cobratoxin〉cytotoxin VII4, and this also relates the order of similarity to the pharmacological properties of theα-conotoxins. Theα-conotoxin-like area of the snakeα-neurotoxins is peripheral to the site previously considered important for binding to the cholinoceptor, even though it seems to represent the focus of evolutionary convergence between the two types of neurotoxin. The area of resemblance does, however, have strong associations with the conformational behavior of the snake toxins. Hence, the outcome of this study has important consequences for the current ideas on snakeα-neurotoxin structure/activity relationships and the evolutionary origins of neurotoxicity.
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    Journal of molecular evolution 10 (1977), S. 155-160 
    ISSN: 1432-1432
    Keywords: Cysteine ; Cystine ; Protein ; Evolution
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    Notes: Summary Analysis of published data on the cysteine and half-cystine content of proteins indicates that most intracellular proteins may be classified as sulfhydryl proteins (those containing cysteine but little or no half-cystine) and that such sulf-hydryl proteins have a low cysteine content. The mean cysteine content found for 32 intracellular mammalian proteins was 1.6 % and intracellular proteins of many bacteria have similar or lower values. Extracellular mammalian proteins are primarily disulfide proteins (those containing half-cystine but little or no cysteine) and have a high half-cystine content, the mean value found for some 34 extracellular mammalian proteins being 4.1 %. This is contrasted with many of the extracellular proteins from facultative bacteria which are cyst(e)ine-free proteins, being lacking in both cysteine and half-cystine. These and related observations are interpreted in terms of the evolution of life in a reducing atmosphere and the subsequent transition to an oxidizing environment. It is suggested that disulfide proteins evolved primarily after the accumulation of oxygen in the atmosphere.
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    Journal of molecular evolution 10 (1977), S. 1-6 
    ISSN: 1432-1432
    Keywords: Evolution ; Ribosomes ; Genotype-Phenotype ; Cytoplasm ; Endosymbiosis ; Procaryote ; Eucaryote ; Progenote
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    Topics: Biology
    Notes: Summary A central evolutionary question is whether the eucaryotic cytoplasm represents a line of descent that is separate from the typical bacterial line. It is argued on the basis of differences between their respective translation mechanisms that the two lines do represent separate phylogenetic trees in the sense that each line of descent independently evolved to a level of organization that could be called procaryotic. The two lines of descent, nevertheless shared a common ancestor, that was far simpler than the procaryote. This primitive entity is called a progenote, to recognize the possibility that it had not yet completed evolving the link between genotype and phenotype. This concept changes considerably the view one takes toward cellular evolution.
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    Journal of molecular evolution 10 (1977), S. 261-264 
    ISSN: 1432-1432
    Keywords: Lysozyme ; Tortoise ; Evolution ; Reptile
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    Topics: Biology
    Notes: Summary A first series of structural studies allowed a reptilian egg-white lysozyme isolated fromTrionyx gangeticus to be classified among the c (chicken) type lysozymes
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    Journal of molecular evolution 11 (1978), S. 1-8 
    ISSN: 1432-1432
    Keywords: Halobacteria ; Archaebacteria ; Phylogeny ; 16S rRNA catalog ; Evolution
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    Topics: Biology
    Notes: Summary Comparative cataloging of the 16S rRNA ofHalobacterium halobium indicates that the organism did not arise, as a halophilic adaptation, from some typical bacterium. Rather,H. halobium is a member of the Archaebacteria, an ancient group of organisms that are no more related to typical bacteria than they are to eucaryotes.
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    Journal of molecular evolution 11 (1978), S. 47-56 
    ISSN: 1432-1432
    Keywords: Genome duplication ; Genome topography ; Evolution ; Gene expression
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    Notes: Summary Genes ofEscherichia coli were grouped according to the “biochemical relatedness” of the enzymes they specifiy, using two schemes to determine relatedness: similarity of reaction or similarity of reactants. The tendency of biochemically related genes as so defined to lie approximately 90° or 180° from one another on the circular genetic map was analyzed statistically. Of the classes analyzed, only the genes for the enzymes of glucose catabolism showed a significant departure from random distribution in this respect. The glucose catabolism genes showed a pronounced tendency to lie either 90° or 180° from one another (P = ca. 10−9), and, furthermore, most of these genes were found to lie in only four gene clusters on theE. coli genome. The significance of this observation is discussed in relation to evolutionary mechanisms and to mechanisms of gene expression.
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    Journal of molecular evolution 11 (1978), S. 313-332 
    ISSN: 1432-1432
    Keywords: Evolution ; Optical activity ; Photolysis ; Circularly ; polarized radiation ; Selection
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    Topics: Biology
    Notes: Summary Stereoselective physical phenomena and their possible importance for the prevalence of D-sugars and L-aminoacids in living matter are reviewed. A classification is presented according to which a selective force provides a microscopic or macroscopic selection depending on its generality when taken over a macrosystem (a ‘unitary biosphere’ such as the Earth). The microscopic ‘selections’ are not genuine selections because the final sense of asymmetry is here determined by chance, in other words the initial choice is ‘random’, while it is ‘directed’ in the macroscopic selection. Two macroscopic selections appear possible: 1. selection due to an intrinsic energy difference between enantiomorph configurations, 2. selection accomplished by elliptically polarised radiation.
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    Journal of molecular evolution 13 (1979), S. 295-304 
    ISSN: 1432-1432
    Keywords: Evolution ; Restriction endonuclease mappings and mitochondrial DNA
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    Notes: Summary A new estimate of the sequence divergence of mitochondrial DNA in related species using restriction enzyme maps is constructed. The estimate is derived assuming a simple Posisson-like model for the evolutionary process and is chosen to maximize an expression which is a reasonable approximation to the true likelihood of the restriction map data. Using this estimate, four sets of mitochondrial DNA data are analyzed and discussed.
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  • 76
    ISSN: 1432-1432
    Keywords: Evolution ; 5S Ribosomal RNA sequences ; Arthropoda ; Secondary structure
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    Notes: Summary 5S Ribosomal RNA sequences have proven to be useful tools in the study of evolutionary relationships among species. However, in reviewing previously published trees constructed from alignments of metazoan 5S RNAs, we noticed several discrepancies with classical evolutionary views. One such discrepancy concerned the phylum Arthropoda, where a crustacean,Artemia salina, seemed to be evolutionarily very remote from four insects. The cause of this phenomenon was studied by determining the 5S RNA sequences of additional arthropods, viz.Limulus polyphemus, Eurypelma californica, Lasiodora erythrocythara, Areneus diadematus, Daphnia magna, Ligia oceanica, Homarus gammarus, Cancer pagurus, Spirobolus sp.,Locusta migratoria, andTenebrio molitor. A tree was then constructed from a dissimilarity matrix by a clustering method known as weighted pair grouping. Application of a correction for unequal evolutionary rates improved the apparent evolutionary position of the arthropods and of some other metazoan species. However, neither the uncorrected nor the corrected tree permitted a completely acceptable reconstruction of metazoan evolution. We presume that this phenomenon is due to random deviations in the evolutionary rate of 5S RNA.
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  • 77
    ISSN: 1432-1432
    Keywords: Glycoprotein ; Evolution ; Ribonuclease
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    Notes: Summary The glycosylation characteristics of the digestive enzyme ribonuclease are summarized. The evolutionary role of this posttranslational modification is discussed and evidence is presented that selection has much influence on the presence or absence of carbohydrate in glycoproteins and on the positions of the carbohydrate attachment sites.
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  • 78
    ISSN: 1432-1432
    Keywords: Ribosomal RNAs ; Cross-hybridization ; Hybridization yield ; Fractional hybridization ; Hybridization homology ; Phylogenetic tree ; Phylogeny ; Evolution ; Archaebacteria
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    Notes: Summary Ribosomal RNAs of 17 species of archaebacteria were hybridized to corresponding and non-corresponding nitrocellulose bound DNAs. The temperature stability of these hybrids and the amount of bound rRNA were determined. A formula was derived to correct the hybridization yields for the different genome lengths and numbers of rRNA operons per genome. This correction made it possible to determine hybridization homologies, as functions of velocity constants, which could then be used in a similar way as sequence homologies. The results were consistent with those from 16S rRNA total sequence data. No correlation was found between the hybridization homologies and the temperature stabilities of the hybrids. This new method is faster and simpler than the method based on total 16S rRNA sequence determination although it provides less total information. Its application to archaebacterial phylogeny has shown theThermococcales to represent a third branch of the kingdom beside the branch of the methanogens + halophiles, and that of theThermoproteales + Sulfolobales. The method has also provided a detailed description of the phylogeny of theSulfolobales showing their origin within theThermoproteales.
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    Journal of molecular evolution 24 (1987), S. 228-235 
    ISSN: 1432-1432
    Keywords: 5S RNA ; Correspondence analysis ; Multivariate statistics ; Evolution ; Phylogeny
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    Topics: Biology
    Notes: Summary Correspondence analysis (a form of multivariate statistics) applied to 74 5S ribosomal RNA sequences indicates that the sequences are interrelated in a systematic, nonrandom fashion. Aligned sequences are represented as vectors in a 5N-dimensional space, where N is the number of base positions in the 5S RNA molecule. Mutually orthogonal directions (called factor axes) along which intersequence variance is greatest are defined in this hyperspace. Projection of the sequences onto planes defined by these factorial directions reveals clustering of species that is suggestive of phylogenetic relationships. For each factorial direction, correspondence analysis points to regions of “importance”, i.e., those base positions at which the systematic changes occur that define that particular direction. In effect, the technique provides a rapid determination of group-specific signatures. In several instances, similarities between sequences are indicated that have only recently been inferred from visual base-to-base comparisons. These results suggest that correspondence analysis may provide a valuable starting point from which to uncover the patterns of change underlying the evolution of a macromolecule, such as 5S RNA.
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    Journal of molecular evolution 24 (1987), S. 236-251 
    ISSN: 1432-1432
    Keywords: 28S rRNA ; RNA secondary structure ; Evolution ; Ribosome ; Translation
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    Topics: Biology
    Notes: Summary We have determined the secondary structure of the human 28S rRNA molecule based on comparative analysis of available eukaryotic cytoplasmic and prokaryotic large-rRNA gene sequences. Examination of large-rRNA sequences of both distantly and closely related species has enabled us to derive a structure that accounts both for highly conserved sequence tracts and for previously unanalyzed variable-sequence tracts that account for the evolutionary differences in size among the large rRNAs. Human 28S rRNA is composed of two different types of sequence tracts: conserved and variable. They differ in composition, degree of conservation, and evolution. The conserved regions demonstrate a striking constancy of size and sequence. We have confirmed that the conserved regions of large-rRNA molecules are capable of forming structures that are superimposable on one another. The variable regions contain the sequences responsible for the 83% increase in size of the human large-rRNA molecule over that ofEscherichia coli. Their locations in the gene are maintained during evolution. They are G+C rich and largely nonhomologous, contain simple repetitive sequences, appear to evolve by frequent recombinational events, and are capable of forming large, stable hairpins. The secondary-structure model presented here is in close agreement with existing prokaryotic 23S rRNA secondary-structure models. The introduction of this model helps resolve differences between previously proposed prokaryotic and eukaryotic large-rRNA secondary-structure models.
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  • 81
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    Journal of molecular evolution 25 (1987), S. 15-19 
    ISSN: 1432-1432
    Keywords: β-Turns ; Secondary structures ; Chirality ; Genetic code ; Biosynthetic pathways ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The physicochemical properties of β-turns suggest their biological importance prior to the formation of the genetic code. These properties include ones potentially affecting the preference for eitherl- ord-amino acids. The abundance of certain amino acids in β-turns is correlated with their assignment to a small, well-defined part of the genetic code and with their role as metabolic precursors for other amino acids. It is proposed that in the prebiotic environment, β-turns became objects of selection that influenced the evolution of the genetic code and biosynthetic pathways for amino acids.
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  • 82
    ISSN: 1432-1432
    Keywords: Balbiani rings ; Evolution ; Immunological detection ; Nucleotide sequence ; 3′ End
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two cDNA clones representing the 3′-end regions of BR1 and BR2 75S mRNA were obtained fromChironomus pallidivittatus. The regular structure characterizing the core of these genes, consisting of tandemly arranged repeat units, changes into a more irregular structure toward the 3′ end. Distal to a standard type of repeat unit with a characteristic excess of positive charges, a new type of repeat with a high, negative charge density is interspersed among parts of the standard unit. The last 111 amino acids before the stop codon represent a unique region distinctly different in amino acid composition from upstream regions, and include two partially homologous hydrophobic regions. Sequence comparison of 3′-end regions from clones representing BR1 and BR2 genes indicates striking sequence conservation in the unique part of the region. Analysis of the level of silent site divergence shows that the homology increases in the 3′ direction up to the polyadenylation site. That the unique region is retained as a part of the secreted protein is shown by Western blotting.
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  • 83
    ISSN: 1432-1432
    Keywords: Histone genes ; Echinoderms ; Maternal mRNA ; Development ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The organization and maternal expression of histone genes differ greatly between the two echinoderm classes represented by the sea stars and sea urchins. We have isolated and characterized a 5.3-kb genomic DNA fragment encoding core histone genes in the sea starPisaster ochraceus. The majority of histone genes are organized as tandem repeats of the 5.3-kb fragment, which is present in as many as 700 copies per haploid genome. The identity, precise location, and transcriptional polarity of individual core histone genes within the repeat were determined by DNA sequence analyses. The gene order in the sea star (H2B, H2A, H4, H3) is different from that in sea urchins (H2B, H3, H2A, H4). What is remarkable is the low level of maternal histone mRNA inP. ochraceus eggs relative to that in sea urchins. This observation supports a recent suggestion that major changes in mode of gene expression, rather than in gene organization or copy number, can be correlated with major events in echinoderm evolution.
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  • 84
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    Journal of molecular evolution 25 (1987), S. 81-88 
    ISSN: 1432-1432
    Keywords: Glutathione ; Evolution ; Phototrophic microorganisms ; Oxygen toxicity
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    Topics: Biology
    Notes: Summary Of the many roles ascribed to glutathione (GSH) the one most clearly established is its role in the protection of higher eucaryotes against oxygen toxicity through destruction of thiol-reactive oxygen byproducts. If this is the primary function of GSH then GSH metabolism should have evolved during or after the evolution of oxygenic photosynthesis. That many bacteria do not produce GSH is consistent with this view. In the present study we have examined the low-molecular-weight thiol composition of a variety of phototrophic microorganisms to ascertain how evolution of GSH production is related to evolution of oxygenic photosynthesis. Cells were extracted in the presence of monobromobimane (mBBr) to convert thiols to fluorescent derivatives, which were analyzed by highpressure liquid chromatography. Significant levels of GSH were not found in the green bacteria (Chlorobium thiosulfatophilum andChloroflexus aurantiacus). Substantial levels of GSH were present in the purple bacteria (Chromatium vinosum, Rhodospirillum rubrum, Rhodobacter sphaeroides, andRhodocyclus gelatinosa), the cyanobacteria [Anacystis nidulans, Microcoleus chthonoplastes S.G., Nostoc muscorum, Oscillatoria amphigranulata, Oscillatoria limnetica, Oscillatoria sp. (Stinky Spring, Utah),Oscillatoria terebriformis, Plectonema boryanum, andSynechococcus lividus], and eucaryotic algae (Chlorella pyrenoidsa, Chlorella vulgaris, Euglena gracilis, Scenedesmus obliquus, andChlamydomonas reinhardtii). Other thiols measured included cysteine, γ-glutamylcysteine, thiosulfate, coenzyme A, and sulfide; several unidentified thiols were also detected. Many of the organisms examined also exhibited a marked ability to reduce mBBr to syn-(methyl,methyl)bimane, an ability that was quenched by treatment with 2-pyridyl disulfide or 5,5′-bisdithio-(2-nitrobenzoic acid) prior to reaction with mBBR. These observations indicate the presence of a reducing system capable of electron transfer to mBBr and reduction of reactive disulfides. The distribution of GSH in phototrophic eubacteria indicates that GSH synthesis evolved at or around the time that oxygenic photosynthesis evolved.
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  • 85
    ISSN: 1420-9071
    Keywords: Evolution ; receptors ; plant hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 86
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    Cellular and molecular life sciences 44 (1988), S. 453-455 
    ISSN: 1420-9071
    Keywords: Adaptation ; diffusion trapping ; sulfate infusion ; PpH ; UpH
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    Topics: Biology , Medicine
    Notes: Summary Upon sulfate administration, UpH falls more in alkalotic rats than in controls. Alkalosis can lead to a reduction in UNH 3V at highly acidic urine. The significance of this process is doubtful at UpH ranging from about 6 to 7. At lower UpH less NH3 would be excreted, thereby less H+ would be trapped in urine and some acid would be conserved.
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  • 87
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    Development genes and evolution 187 (1979), S. 105-127 
    ISSN: 1432-041X
    Keywords: Drosophila ; Pattern formation ; Leg ; Bristle ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The bristle pattern of the second-leg basitarsus inDrosophila melanogaster was studied as a function of the number and size of the cells on this segment in well-fed and starved wild-type flies, in triploid flies, and in two mutants (dachs andfour-jointed) that have abnormally short basitarsi. The second-leg basitarsi of well-fed, wild-type flies from 22 otherDrosophila species were studied in a similar manner. There are typically 8 longitudinal rows of evenly-spaced bristles on the second-leg basitarsus, and in each row the number of bristles was consistently found to vary in proportion to the estimated number of cells along the segment, and the interval between bristles was found to vary in proportion to the average cell diameter on the segment. These correlations are interpreted to mean that the spacing of the bristles within each row is controlled developmentally, whereas the number of bristles is not. The interval between bristles is evidently measured either as a fixed number of cells or as a distance which indirectly depends upon cell diameter.
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  • 88
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    Cellular and molecular life sciences 42 (1986), S. 134-136 
    ISSN: 1420-9071
    Keywords: Adaptation ; animal models ; animal vendor effects ; evolutionary mechanisms ; rat strain effects ; rat swimming ; sleep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Over the past few years, our laboratory group has elaborated a repeated measures rat swimming test. It provides an animal base for showing that the REM sleep mechanism is important to both emotional responsiveness and environmental adaptations. All of that work has been done with Sprague-Dawley rats obtained from a local supplier. Work done with two European rat stocks (by researchers in France and The Netherlands) shows general agreement with our own. In this presentation, we directly compare rats derived from an English vendor's Sprague-Dawley stock with the U.S. based Sprague-Dawley stock which we have been using. We also make strain comparisons via the F344 and the Long Evans strains. Although the literature has numerous examples of swimming test differences between inbred and wild rat stocks, strain difference effects have not been reported. We report that there are significant differences attributable to inbred strain but not to vendor on this measure.
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  • 89
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    International journal of biometeorology 33 (1989), S. 246-250 
    ISSN: 1432-1254
    Keywords: Sweating in calves ; Age and heat tolerance ; Sweating, age effects ; Sweating, seasonal effects ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Sweating rate, rectal and skin temperatures and respiration rate were measured at weekly intervals from 7 days of age (for 4 weeks in Experiment 1; 6 weeks in Experiment 2) in winter- and summer-born Friesian calves exposed to a temperature of 39°C dry bulb and 32°C wet bulb in a climate chamber. Four calves were studied in each season in both experiments. In Experiment 1, ambient temperatures were from 3° to 9°C higher in early summer than in late winter. During each 39°C exposure, sweating rate increased from basal levels of 40–90 to plateau levels of 120–300 g/m2 per h after 90–120 min. The increase in sweating rate with age was most pronounced in winter-born calves, but summer-born calves had higher values at 1 week of age (167±52.4 vs 94.4±30.1 g/m2 per h). Seasonal differences in ambient temperature were greater in Experiment 2 (11° to 17°C). In this case summer-born calves had higher sweating rates at each age (plateau values of 220–320 g/m2 per h), and showed a more rapid increase in sweating rate during each 39°C exposure than winter-born calves (plateau values of 100–250 g/m2 per h). The results demonstrate major changes in sweating competence during the first 4–6 weeks of life in Friesian calves, a quite pronounced effect of season (ambient temperature) on the levels of sweating achieved, and indicate that low sweating rates in newborn calves are a contributing factor in deaths due to hyperthermia in semi-arid grazing areas.
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  • 90
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    Oecologia 72 (1987), S. 69-76 
    ISSN: 1432-1939
    Keywords: Cabbage butterfly ; Pieris rapae ; Evolution ; Adaptation ; Colonisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Australian and U.K. Pieris rapae differ markedly in their oviposition behaviour; U.K. females produce a more aggregated egg distribution, and lay their eggs more quickly, than do Australian females. The adaptive reason for this divergence probably lies in the relative costs of increased flight time (more costly in the U.K.) and increased local crowding (more costly in Australia). There is also a strong relationship between juvenile developmental rate (at constant temperature) and oviposition behaviour, but the form of this relationship differed between the two populations. The adaptive reasons for the link between developmental rate and behaviour is not clear. It may be that this link represents the tip of the iceberg; i.e. that physiological, developmental, and behabioral characters all co-vary in ways and for reasons that we do not yet understand.
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  • 91
    ISSN: 1432-1939
    Keywords: Adaptation ; Speciation ; Urine ; Kidney ; Spalax ehrenbergi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report on kidney structure and function in subterranean mammals of four chromosomal species (2n=52, 54, 58 and 60) belonging to the Spalax ehrenbergi superspecies, in relation to their speciation and adaptive radiation from mesic (2n=52) to xeric (2n=60) environments in Israel. Structural variables measured involved: (1) Relative Medullary Thickness, (RMT); (2) Relative Kidney Weight. (RKW); and (3) Percentage of Kidney out of Body Weight (PKW). Functional variables involved: (i) Urine Solid Concentration, (USC); and (ii) Urine Osmotic Concentration (UOC). The results for chromosomal species 2n=52, 54, 58 and 60 indicated nonsignificant increase southward for RMT, but displayed significant increase along the same transect for RKW, PKW, and USC. The UOC was significantly lower in mesic 2n=52 as compared to the other three species when experimental animals were fed in the laboratory on regular carrot food. However, protein stress food (soybean) and salt stress of 0.45 mol NaCl, caused significant, three and a half fold increase of UOC in 2n=52, 54 and 58; but four and a half fold increase in 2n=60, significantly higher than in the other three species. We conclude that both structurally and functionally, the kidneys differentiated adaptively during the Pleistocene evolution of S. ehrenbergi in Israel, in accordance with aridity stress and halophyte food resources towards the desert. Nevertheless, Spalax generally shows clear upper limits in kidney structural and functional capacities, preventing it from colonizing the true desert, south of the 100 mm isohyete.
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  • 92
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    Oecologia 76 (1988), S. 553-561 
    ISSN: 1432-1939
    Keywords: Adaptation ; Carbon isotope ratio ; Leaf conductance ; Water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Encelia farinosa and Encelia frutescens are drought-decidous shrubs whose distributions overlap throughout much of the Sonoran Desert. During hot and dry periods, leaves of E. farinosa utilize increased leaf reflectance to reduce leaf temperature, whereas leaves of E. frutescens have substantially higher leaf conductances and rely on increased transpirational cooling to reduce leaf temperature. E. farinosa is common on the dry slope microhabitats, whereas E. frutescens occurs only in wash microhabitats where greater soil moisture is available to provide the water necessary for transpirational cooling. E. farinosa tends not to persist in wash microhabitats because of its greater susceptibility to flashfloods. The consequences and significance of increased leaf reflectance versus increased transpirational cooling to leaf temperature regulation are discussed.
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  • 93
    ISSN: 1432-1939
    Keywords: Developmental rate ; Adult weight ; Adaptation ; Temperature ; Acyrthosiphon pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Developmental rate and adult weight were studied at constant temperatures from 9.8 to 27.9°C for 18 clones from each of five populations of the pea aphid, Acyrthosiphon pisum (Harris), from locations between 39 and 53°N latitude in central North America. The response of developmental rate to temperature for each clone was accurately described by a three parameter non-linear equation. Adult weight usually decreased with increasing rearing temperature, but the shape of the response to temperature varied among clones. Variation in the developmental parameters was greater among clones within populations than among populations. No consistent trends were observed in the developmental parameters or adult weights either with latitude or the long term average temperatures at the locations. We conclude that previously reported geographic variation in the developmental threshold of this species, which was attributed to local adaptation, occurred either because the clones tested were not representative of the populations or because rearing methods differed among studies. The results are discussed in relation to the hypothesis that life history traits which are temperature sensitive are adapted to local thermal environments.
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  • 94
    ISSN: 1432-1939
    Keywords: Acyrthosiphon pisum ; Migration ; Adaptation ; Photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The purpose of the study was to quantify long distance movements in populations of pea aphid, Acyrthosiphon pisum (Harris), by estimating origins and distances travelled by immigrants into a southern Manitoba population. A strong relationship was demonstrated between latitude of origin and photoperiods at which pea aphid populations are stimulated to produce the diapause stage (Smith 1987). Therefore, the approach was to use photoperiodic response as a physiological marker to identify the source of immigrant aphids. The responses of 89 clones from Glenlea, Manitoba (49°38′N), sampled 5 times over 2 seasons, were measured. One sample of clones collected the first season had photoperiodic responses similar to those of a population about 300 km to the south, and significantly different from clones collected in spring of the same year at the same site. Weather analysis corroberates that the migrants were probably carried into Manitoba on a southerly flow of air during the previous 24 to 36 h.
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  • 95
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    Oecologia 76 (1988), S. 161-167 
    ISSN: 1432-1939
    Keywords: Adaptation ; Altitudinal gradients ; Herbivores ; Insect galls ; Species richness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five hypotheses were invoked to account for variation in galling species number per location on plants of different structural complexity, namely herbs, shrubs, and trees, both in Brazil and USA. The hypotheses were: 1) the altitudinal/latitudinal gradient hypothesis; 2) the harsh environment hypothesis; 3) the plant species richness hypothesis; 4) the host plant area hypothesis; 5) the plant structural complexity hypothesis. The altitudinal and the harsh environment hypotheses were correlated and supported with sample data in both localities, with increasing gall species number as altitude/latitude declined and as sites became hotter and drier. The two hypotheses were separated by studying riparian sites and dry hillside sites at the same elevation in Arizona. Galling species frequency was higher in dry sites than in riparian sites, supporting the harsh environment hypothesis. Of the five hypotheses tested only the harsh environment hypothesis predicted that galling insect species number should vary in response to environmental variables such as moisture and temperature. Temperate shrubs supported more galling species than did other plant types, both in dry and mesic sites. The overall difference between galling species richness for tropical and temperate latitudes was not statistically significant. Free-feeding insect herbivore species exhibited the opposite pattern of species richness to gallers, being more speciose in riparian sites. The present study corroborates the hypothesis that the gall forming habit is an adaptation to harsh or stressful environments, and we describe for the first time broad scale geographical patterns in galling insect species richness.
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  • 96
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    Oecologia 77 (1988), S. 533-536 
    ISSN: 1432-1939
    Keywords: Energetics ; Speciation ; Adaptation ; Spalax ehrenbergi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Gross energy intake and apparent dry matter digestibility of animals fed carrots ad lib in the laboratory, were measured in the four chromosomal species of the Spalax ehrenbergi superspecies in Israel. Gross energy intake of 132.8 and 155.9 kJ/day was measured for the 2n=52 and 2n=58 chromosomal “mesic” species, while in the 2n=54 and 2n=60 chromosomal “xeric” species it measured only 80.3 and 75.0 kJ/day, respectively. Dry matter digestibility ranged between 92.3 and 95.6% in thefour chromosomal species. The differences in gross energy intake between the “mesic” and “xeric” species, appeared to reflect adaptive energy metabolism variation associated with geographic variation in climate, habitat productivity, and food availability.
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  • 97
    ISSN: 1432-0983
    Keywords: Crithidia fasciculata ; rRNA ; Sequence ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We present the cloning and sequence analysis of the nuclear-encoded Crithidia fasciculata small subunit (SSU) rRNA gene, the longest (2,206 bp) such gene yet characterized by direct sequence analysis. Much of the sequence can be folded to fit a phylogenetically conserved secondary structure model, with the additional length of this gene being accommodated within discrete variable domains that are present in eukaryotic SSU rRNAs. On the basis of sequence comparisons, we conclude that Crithidia contains the most highly diverged SSU rRNA described to date among the eukaryotes, and therefore represents one of the earliest branchings within the eukaryotic primary kingdom.
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  • 98
    ISSN: 1432-0983
    Keywords: ATP synthase β ; Selective constraint ; mtDNA ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have cloned and sequenced human and bovine cDNAs for the β subunit of the ATP synthase (ATP-synß), a nuclear DNA (nDNA) encoded oxidative phosphorylation (OXPHOS) gene. The two cDNAs were found to share 99% amino acid homology and 94% nucleotide homology. The evolutionary rate of ATPsynß was then compared with that of two mitochondrial DNA (mtDNA) ATP synthase genes (ATPase 6 and 8), seven other mtDNA OXPHOS genes, and a number of nuclear genes. The synonymous substitution rate for ATPsynß proved to be 1.9 × 10−9 substitutions per site per year (substitutions × site−1 × year−1) (SSY). This is less than 1/2 that of the average nDNA gene, 1/12 the rate of ATPase 6 and 8, and 1/17 the rate of the average mtDNA gene. The synonymous and replacement substitution rates were used to calculate a new parameter, the “selective constraint ratio”. This revealed that even the most variable mtDNA protein was more constrained than the average nDNA protein. Thus, the high substitution mutation rate and strong selective constraints of mammalian mtDNA proteins suggest that mtDNA mutations may result in a disproportionately large number of human hereditary diseases of OXPHOS.
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  • 99
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    European biophysics journal 3 (1977), S. 141-143 
    ISSN: 1432-1017
    Keywords: Calcium ; Limulus ; Photoreceptors ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Calcium ion fulfills several criteria for identifying an intracellular messenger for light-adaptation in Limulus photoreceptors. Direct injection of Ca++ mimicks two aspects of light-adaptation; sequestration of intracellular calcium tends to prevent light-adaptation; and light induces an increase in intracellular Ca++ as demonstrated by two independent techniques.
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    European biophysics journal 3 (1977), S. 171-173 
    ISSN: 1432-1017
    Keywords: Adaptation ; Frog ; Retina ; Rhodopsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Rod dark adaptation in the amphibian retina appears to be due to three processes: 1. background adaptation, occurring immediately after the extinction of an adapting or bleaching light, 2. intermediate adaptation, that frequently lasts 30 min or more and 3. opsin adaptation, which in the isolated retina where regeneration of rhodopsin is insignificant, is observed as a permanent loss of sensitivity after the completion of intermediate adaptation. Intermediate adaptation is characterized by a linear relation between log threshold and the amount of “retinal” present, a similar relation is obtained between log threshold and the amount of rhodopsin bleached in opsin adaptation. These adaptation processes are discussed in terms of a model of the rod outer segment.
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