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  • Springer  (93)
  • American Institute of Physics (AIP)  (3)
  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The iron storage ferritin light-chain gene exhibits multiple restriction enzyme fragments which have been mapped by analyzing sorted human chromosomes. A dual laser chromosome sorter was used to construct spot-blot filter panels representing 22 chromosome fractions. Hybridization of radiolabeled human ferritin-L gene probe to spot-blot panels revealed the ferritin-L gene on more than one chromosome. Miniaturized restriction enzyme analysis was used to map each of the ferritin-L restriction fragments uniquely to one of three chromosomes. This combination of sorted chromosome analyses provides a rapid method to map homologous DNA sequences located on more than one chromosome.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 41 (1971), S. 79-84 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Untersuchungen der Polymorphismen in natürlichen Populationen von A. barbata im kalifornischen Weideland hatten einerseits zum Nachweis eines weit verbreiteten Monomorphismus und andererseits streng lokalisierter polymorpher Bereiche in der nördlichen Küsten- und San Francisco-Region geführt, wobei eine Anzahl morphologischer und isoenzymatischer Markerloci zugrunde gelegt wurde. Da diese Art, wie viele andere Annuelle auch, während der spanischen Missionsperiode aus der Mittelmeerregion eingeführt wurde, wurde eine vergleichende Untersuchung der Canadian-Welsh-Sammlungen von Avena-Arten aus der Mittelmeerregion anhand verschiedener Merkmale der Pflanzen und der Stärkegelelektrophorese-Untersuchung auf Esterase-, Phosphatase- und Peroxydase-Systeme durchgeführt. Es wurde eine Gesamtheit von 96 Stichproben, bestehend aus 73 A. barbata und 23 A. hirtula, untersucht und die Ergebnisse zur Berechnung von Polymorphismus-Indices verwendet. In beiden Arten zeigten nur 10 bis 15% der Herkünfte einen signifikanten Polymorphismusgrad. Von ihnen scheint die Mehrzahl von lokalisierten Regionen in Italien und Griechenland abzustammen. Ein Teil des beobachteten Fehlens einer Variation innerhalb der Stichproben könnte eine Folge des geringen Stichprobenumfangs sein. Im allgemeinen scheinen die Variationsmuster der kalifornischen Untersuchungen und die der vorliegenden Analysen von A. barbata sehr ähnlich zu sein. Das führt zu einigen interessanten Fragen nach a) der Besiedelungsgeschichte des eingeführten Materials, b) den Faktoren, die derart auffallenden Mustern der geographischen Variation unterliegen und c) den laufenden evolutionären Änderungen, die in diesen beiden großen, voneinander getrennten Gebieten der Artverteilung auftreten.
    Notes: Summary Surveys for polymorphisms in natural populations of A. barbata sampled in California grasslands had provided evidence for widespread monomorphism and rather localized polymorphic areas in the north coastal and San Francisco regions, based on a set of morphological and isoenzymatic marker loci. Since this species, like many other annuals, was introduced from the Mediterranean region during the Spanish mission period, a comparative study of the Canadian-Welsh collections of Avena species from the Mediterranean region was undertaken using various plant characters and starch gel electrophoresis to analyze variants for esterase, phosphatase and peroxidase systems. A total of 96 samples including 73 of A. barbata and 23 of A. hirtula were studied and the results were scored to compute the polymorphism indices. In both species, only 10 to 15 percent sites showed any significant degree of polymorphism of which a majority seemed to originate from localized regions in Italy and Turkey; a part of this observed lack of within-sample variation might be the result of small sample size. In general, the patterns of variation in A. barbata from the California surveys and the present analyses seemed to be very similar and raised some interesting questions on (a) the colonizing history of introduced materials (b) the factors underlying such marked patterns of geographical variation, and (c) the current evolutionary changes occurring in these two broad, disjunct areas of species distribution.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 44 (1974), S. 7-11 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The population structure of wild oats (Avena fatua) sampled in two prune orchards was described using Wright's model of a population having many largely isolated, small subdivisions. A high degree of genetic differentiation was observed among the individual colonies for lemma color, leaf sheath hairiness and isoenzymatic loci. Estimates of genotypic frequencies and population sizes over a two-year period suggested that random drift played an important role in the population changes toward a highly mosaic pattern of differentiation and local monomorphism in a substantial proportion of colonies. It was recognized, however, that without additional extensive field studies, the hypothesis of irregularly dispersed factors of multiniche selection could not be ruled out. Similar studies are briefly reviewed in order to outline the research needed on the issue of selection versus random drift as the primary force in local differentiation.
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  • 4
    ISSN: 1432-2242
    Keywords: Evolution of inbreeding ; Electrophoretic variation ; Phenotypic plasticity ; Variation patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several populations of two species of the genus Limnanthes, (L. alba, an outbreeder and L. floccosa, an inbreeder) were examined with respect to variability of fifteen quantitative characters, allozyme variation at 11 loci, and response to different pollination conditions and moisture stress. Nearly equal amounts of phenotypic variability were found in the two species. L. alba had higher within-family variability than L. floccosa, but this result was highly heterogeneous among characters. A study of between- and within-population variance estimates did not reject the null hypothesis that L. alba and L. floccosa are similar with regard to the partitioning and amount of variability for quantitative characters. However, allozyme variation at 11 loci in a large number of populations showed L. alba to be highly polymorphic in contrast to the virtual monomorphism within L. floccosa populations. The average number of alleles per locus in L. alba and L. floccosa was 1.97 and 1.02, respectively, and on an average, L. alba and L. floccosa populations had 63% and 3% loci with polymorphism, respectively. Three groups of allozyme allelic combinations emerged which correlated well with the taxonomic delineation of allogamous L. alba, three semi-autogamous L. floccosa forms and two autogamous L. floccosa forms. All taxa showed a significant reduction in the seed output per plant due to moisture stress. L. alba suffered a further loss of fecundity under the paucity of pollinators, L. floccosa ssp. floccosa showed no significant effect from this factor, whereas L. floccosa ssp. grandiflora exhibited a curvilinear response which peaked at ‘partial pollination’ and decreased to a lower level at ‘full pollination.’ The geographic distribution of the two species with regard to the temperature and rainfall distribution did not suggest L. floccosa to be living in drier marginal areas. Patterns of variation in flowering time showed L. alba to be less variable than L. floccosa. Overall, there seemed to be little direct support for the thesis that inbreeding species originated from outcrossing taxa in marginal environments as a direct adaptation to a shortened growing season of xeric environments and to the lack of pollinators. Alternative hypotheses suggest that autogamy in L. floccosa might have evolved as a reproductive isolating barrier acting through either cleistogamy or divergence in flowering times.
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  • 5
    ISSN: 1432-2242
    Keywords: Allozyme variation ; Genetic distance ; Speciation ; Systematics ; Population genetic hypotheses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An electrophoretic survey of genetic variation in 50 populations representing all ten taxa of section Inflexae of the plant genus Limnanthes is reported here with three objectives: 1) to describe genetic differentiation for testing certain phylogenetic hypotheses on the origin of species and infraspecific relationships, 2) to evaluate the concordance of electrophoretic, morphological and hybridization data within the section, and 3) to discuss models of speciation using Limnanthes as an example. Species, subspecies, and populations, designated on the basis of morphology and distribution, gave decreasing values of genetic distances that were apparently maintained across a wide ecological and geographical range. Using electrophoretic, morphological and hybrid fertility data, we concluded that L. montana, intermediate in range between the two disjunct varieties of L. gracilis, is not likely to be a relictual set of populations from what once was a continuously distributed taxon as hypothesized by earlier workers. Neither L.g. gracilis nor L.g. parishii appear to have been founded by long distance dispersal from one to the other. However, a very close genetic relationship was detected between L. gracilis and L. alba. This genetic pattern suggested that the two disjunct L. gracilis varieties were probably connected by a L. alba-like taxon and perhaps originated from that taxon. Evidence based on allozyme variation did not support the thesis that the inbreeder L. floccosa is a recent derivative from the outbreeder L. alba. Among the remaining five taxa (i.e. two varieties of L. gracilis, two varieties of L. alba, and L. montana), genetic distance and interspecific hybridization data are highly concordant, (r = -0.92, P 〈 0.001). The agreement of these two approaches with species relationships based on morphological similarity was less certain. Limnanthes species appear to exhibit greater interpopulation differentiation than many plant groups, perhaps a reflection of their distinctive island-like distribution pattern. On the other hand, an unusually high crossability is found in Limnanthes. Speciation in Limnanthes appears largely to follow a model of adaptive geographical divergence but certain other modes cannot yet be ruled out.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 71 (1985), S. 292-299 
    ISSN: 1432-2242
    Keywords: Breeding system ; Population subdivision ; Multilocus estimator ; Inbreeding ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The breeding systems of seven Limanthes (Limanthaceae) populations, including one “inbreeding” and three “outbreeding” taxa, were quantified using a multilocus outcrossing rate estimator (tm) and autofertility estimates. Along with the assays of heterozygosity levels, these data were used to separate components of “effective” outcrossing in terms of Wright's equilibrium inbreeding coefficient (Fe) and adult (FA) and zygotic (FZ) fixation indices. The patchy distribution of alleles as a potential source of “substructure inbreeding” was tested from the allelic frequencies mapped along a linear transect. Evidence for consanguineous matings in restricted neighborhoods and for selection at two different life cycle stages, and the efficiency of the protandrous breeding system were noted and discussed. Multilocus estimates of outcrossing are useful for their greater precision and unbiased nature while single locus estimates can help in detecting the effects of selection and population substructure. The data generally support the “heterozygosity paradox” noted by Brown (1979) but further suggest that the paradox may often result from a lack of precision of outcrossing estimates and from overlooking the stages of the life cycle being sampled.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 38 (1968), S. 232-242 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die gemeinsamen Effekte der Koppelung, Inzucht und zufälligen genetischen Drift werden hinsichtlich der Populationsveränderung unter Selektion unter Einschluß von Geninterktionen untersucht. Für die Monte-Carlo-Simulationen wurde ein 6-Locus-Modell mit einem einheitlichen Ausmaß der Rekombination zwischen benachbarten Paaren von Loci, gemischter Selbstung und Panmixie und dreier Grundtypen der Selektion (heterotisch, optimalisierend und gemischt optimalisierend-heterotisch) benutzt. Die Ergebnisse werden in erster Linie in Termini der Gendispersion, der genetischen Variabilität, der Gameten-Unbalance (Koppelungs-Ungleichgewicht) und der Näherung an stabile Genfrequenz-Gleichgewichte beschrieben. Sowohl unter kumulativen wie auch unter diminutiven Heterosis-Modellen kann ein stabiler Zustand des Polymorphismus erreicht werden, wobei die zufällige Gendispersion klein ist und verschiedene wiederholte Populationen einen hohen Grad gametischer Unbalance entwickeln, die sich in einem Überschuß entweder der Attraktionsoder der Repulsionsphase in Abhängigkeit von der zufälligen Drift in der Genfrequenz äußert. Auf der anderen Seite erleiden alle Populationen unter dem Optimum-Modell einen stetigen Verfall in Richtung auf Fixierung aller Loci, obwohl die Gendispersion durch ziemlich komplexe Interaktionen zwischen Parametern für Selbstung, Koppelung und Selektionsintensitäten beeinflußt wird. Die Gendispersion war bei höherem Inzuchtgrad nicht notwendigerweise höher. In allen Läufen mit Optimum-Modellen, in denen sich die mittlere Populations-Fitness dem Wert 1 nähert, wurde ein Überschuß von Typen mit Repulsionskoppelung beobachtet, vor allem bei enger Koppelung und starker Inzucht. Jede Asymmetrie in dem Sinne, daß Selektion das eine oder das andere Allel begünstigt, begünstigt zugleich die Genfixierung besonders bei Vorliegen von Inzucht. Auf der anderen Seite scheint ein Heterozygotenvorteil hinsichtlich der Erhaltung der Heterozygotie eine relativ größere Rolle bei Vorliegen von Inzucht zu spielen. Gemischte Optimum-heterotische-Modelle liefern einen Kompromiß zwischen den divergierenden Attributen multilokaler Systeme hinsichtlich der Erhaltung der Polymorphismen und der Maximalisierung der Fitness im Vergleich zu bestimmten optimal gekoppelten Genkomplexen. Im allgemeinen stimmen diese Ergebnisse, wie erwartet, bei mittlerem bis großem Populationsumfang mit denen früher für deterministische 2-Locus-Modelle berichteten überein.
    Notes: Summary The joint effects of linkage, inbreeding, and drift due to finite population size were investigated in terms of population changes under selection involving gene interaction. Six-locus models with the same amount of recombination between adjacent pairs of loci, mixed selfing and random mating, and selection of basically three forms (heterotic, optimizing and mixed optimum-heterotic) were used for Monte Carlo simulation. The results were primarily described in terms of certain measures of gene dispersion, genetic variability, gametic unbalance (linkage disequilibrium) and the approach to stable gene frequency equilibria. Under both cumulative and diminutive heterosis models, a steady state with polymorphisms could be attained with random gene dispersion being small and different replicate populations evolved high degrees of gametic unbalance in the direction of excess of either coupling or repulsion phase linkages depending on the random drift in gene frequencies. Under optimum models, on the other hand, all populations approached steady decay toward fixation at all loci although gene dispersion was governed by rather complex interactions between the parameters of selfing, linkage and selection intensity. Gene dispersion was not necessarily proportionately greater with the higher levels of inbreeding. An excess of repulsion linkages with mean population fitness approaching unity was noted in all runs with the optimum models, more so with tight linkage and heavy inbreeding. Any asymmetry in the sense of selection favoring one or the other allele tends to reinforce gene fixation particularly under inbreeding. Heterozygote advantage, on the other hand, seemed to play a relatively greater role under inbreeding in terms of retaining heterozygosity. Mixed optimum-heterotic models provide a favorable compromise between these conflicting attributes of multilocus systems in terms of the maintenance of polymorphisms and the maximization of fitness in relation to certain optimal linked gene complexes. In general, for moderate to large population size these results are, as expected, in line with those reported previously for two-locus deterministic models.
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  • 8
    Electronic Resource
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    Springer
    Theoretical and applied genetics 40 (1970), S. 73-75 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Je 20 Familien von Avena fatua und A. barbata, die aus natürlichen Populationen entnommen worden waren, wurden zur Messung der Reaktion auf intrafamiliäre Selektion auf die beiden Extreme des Schoß-Termins und der Samengröße verwendet. Die Schätzungen der relativen Beiträge der Variation zwischen und innerhalb der Familien wurden in Beziehung zu der erzielten Reaktion interpretiert, um zu zeigen, daß A. fatua eine größere genetische Variabilität und A. barbata eine größere phänotypische Plastizität als die jeweils andere Art besitzt. Die vorliegenden Ergebnisse stützen unser früher diskutiertes Modell der alternativen adaptiven Strategien in diesen beiden Spezies.
    Notes: Summary Twenty families each of Avena fatua and A. barbata drawn from a natural population were used for measuring the response to within-family selection for the two extremes in heading date and seed size. The estimates of the relative amounts of between- and within-family variation were interpreted in relation to the realized responses to show that A. fatua has greater genetic variability than A. barbata which, on the other hand, has more phenotypic plasticity. These results support our model on the alternative adaptive strategies in the two species discussed earlier.
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  • 9
    ISSN: 1432-2242
    Keywords: Amaranths ; Biosystematics ; Agronomic Potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three weedy amaranths (Amarantkus hybridus, A. retroflexus and A. powellii) from nine California sites, three domesticated species (A. caudatus, A. hypochondriacus and A. cruentus) from the USDA plant inventory as well as other sources and a naturally-occurring crop-weed hybrid were studied for numerical taxonomy using morphological and allozyme variation data. The crop and weedy species groups were easily separated and the hybrid populations were found to be intermediate. Surprisingly, very little intraspecific variation was present. Crop, weed and hybrid amaranths were also compared for their yielding ability, harvest index, seed efficiency of grain production and protein, popping quality and other agronomic traits. Although field plot yields were similar among the three groups of species (700 Kg/ha seed without fertilizer treatment and water, ranging to 3000 Kg/ha with fertilizer applications of 170 Kg N/ha, and abundant water), the harvest index of the weedy group was much higher (25–40%) than the domesticated species (10–15%). The allocation of biomass to seed production is positively correlated with seed yield in the domesticated but not in the weedy types, whereas the percentages of biomass as stem material and as seeds are negatively correlated. Several weedy and crop characteristics together should provide the basis of new improved cultivars through genetic recombination and selection.
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  • 10
    ISSN: 1432-2242
    Keywords: Gynodioecy ; Colonizing species ; Mating system ; Isozymes ; Population structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A multilocus procedure was used to estimate outcrossing rates in ten roadside populations of Trifolium hirtum in California. Three groups of populations were studied: cultivars, hermaphroditic, and gynodioecious (sexually dimorphic) populations. The multilocus outcrossing rate (tm) varied from 0.05 to 0.43 among populations. Population level tm estimates were significantly correlated with the observed heterozygosity in gynodioecious populations but not in hermaphroditic populations. The outcrossing rate of hermaphrodites and females was estimated in three gynodioecious populations; the estimates of tm varied from 0.09 to 0.23 for hermaphrodites and from 0.73 to 0.80 for females. The distribution of outcrossing rates in gynodioecious populations is bimodal. Our results indicate that for the levels of selfing observed among hermaphrodites, inbreeding depression is likely to be a major factor in the maintenance of females in gynodioecious populations.
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