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  • 1965-1969  (7)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 22 (1967), S. 391-400 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The morphology and pattern of replication in the somatic chromosomes of Leptodactylus ocellatus (Amphibia, Anura) was studied by means of H3-thymidine autoradiography. A total of 300 metaphases from leukocyte cultures and 200 metaphases from spleen cell cultures were analysed. The diploid chromosome number in Leptodactylus ocellatus is 22. The pairs 1, 2, 3, 4, 7 and 8 could be easily identified on the basis of their size, centromere position, and location of secondary constrictions. In 30% of metaphases the pair 10 could be recognized on account of an end-to-end homologous association, which originated from a satellite fusion. The continuous H3-thymidine labelings carried out in the last 10, 5 and 3 hours of a culture indicated that the G2 period was 3.5 hours. The labeled metaphases were divided in two groups. In the first one all those cells showing radioactivity along the entire length of every chromosome were included. The second group was formed by metaphases with extensive unlabeled chromosome regions. The former and the latter group were identified as representatives of the intermediate and final stages of the S period, respectively. The pattern of chromosome labeling indicates that secondary constrictions are associated with late replicating regions. However, the presence of chromosome areas, which in spite of being late in finishing duplication did not bear any kind of constriction, suggests that regions other than those associated with constrictions also may replicate late. No interchromosomal asynchrony of replication at the end of the S period was noticed. However, very often in pair 10 one chromosome had about two times as much labeling as its homologue. No sex-linked differences in chromosome morphology or in patterns of chromosome replication could be noticed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Chromosome measurements were performed in four species of snakes related at the level of suborder (Boa constrictor amarali, Xenodon merremii, Philodryas patagoniensis, Bothrops jararaca). The data obtained point out that pairs 1–3 were common to the four snakes and probably inherited from the ancestor of the suborder Serpentes. Pairs 5–8-W were characteristic of each snake; hence, it is possible to assume that they followed evolving after the appearing of the suborder Serpentes. Z-chromosomes were metacentric in B. constrictor amarali, X. merremii and B. jararaca and slightly submetacentric in P. patagoniensis. Area of these chromosomes varied from 8.6–10.6% of the haploid set in the four species studied.-The study of chromosome replication at the end of the S period points out that “shared chromosomes” have similar patterns of labeling. Therefore, it is proposed that the distribution of late replicating regions and heterochromatin in the genome is phylogenetically transmitted and probably genetically determined.—The analysis of the ending-sequence of chromosome replication shows that sex chromosomes finish earlier than macroautosomes. It is concluded that snakes probably have no mechanism of sex chromosome heterochromatinization in either sex. The absence of late replicating Z-chromosome in the males, favours the hypothesis that no mechanism of sex dosage compensation is acting in the suborder Serpentes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 28 (1969), S. 370-378 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The chronology of Y chromosome replication in meiosis of male adult rats was investigated. 3HTdR was injected into the testes and animals were sacrificed at 2-hour intervals from 2 to 24 hour after the injection; and at 2-day intervals from 2 to 64 days after the injection. Autoradiograms from germ line cell spreads were prepared. The study of spermatogonial metaphases showed that the Y chromosome is the last to begin and end DNA synthesis. Consequently, by detecting such a pattern of replication it was possible to trace the asynchronous Y from spermatogonia to sperm. Assuming that Y chromosomes are early replicating in preimplantation embryos of mammals it is proposed that Y chromosome of rats shift from late to early replicating in the first divisions of the fertilized egg. Moreover, the analysis of the patterns of sperm labeling allow one to infer that chromosomes are end-to-end associated in sperm nuclei, and that the Y chromosome and perhaps autosomes as well occupy a constant position in sperm of rats.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 25 (1969), S. 1111-1112 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Resumen Se estudiaron los cromosomas de 16 ejemplares deRattus rattus provenientes de la Provincia de Buenos Aires (Argentina) y del Estado de Rio Grande do Sul (Brasil). En todos los animales el complemento estuvo formado por 38 cromosomas. Considerando que en las ratas el complemento de 42 cromosomas es probablemente el mas generalizado, se sugiere que el complemento de 38 cromosomas ha derivado del de 42 mediante un proceso de reordenamiento cromosómico con fusión céntrica.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 25 (1969), S. 1210-1211 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Resumen Se han estudiado los cromosomas de dos especies de didélfidos del géneroMonodelphis: M. brevicaudata palliolata del norte de Venezuela yM. dimidiata de la Prov. de Buenos Aires, Argentina. Ambas especies tienen un cariotipo muy similar, compuesto de 18 cromosomas. Este cariotipo es intermedio entre el que presentanCaluromys yMarmosa (2n=14) y el deDidelphis, Philander yLutreolina (2n=22). Se postula la fisión céntrica en dos pares de submetacentricos del primer tipo, para explicar el origen del cariotipo deMonodelphis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 53 (1966), S. 590-591 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 38 (1968), S. 343-347 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung An der FeldmausAkodon azarae wurde die Länge der Geschlechtschromosomen, die Größe des Geschlechtschromatinkörperchens und das Muster der Geschlechtschromosomenreplikation bestimmt. Unter den untersuchten Tieren befand sich auch eine Gruppe von Weibchen mit einem spontan deletierten X-Chromosom. Der Karyotyp dieser Weibchen war 38 Xx, wobei x das stark deletierte X-Chromosom darstellt. Die Länge der Geschlechtschromosomen wurde wie folgt, ausgedrückt in Prozent des haploiden Satzes, ermittelt: X-Chromosom 7,89% (±1,18), x-Chromosom 1,47% (±0,20), Y-Chromosom 1,15% (±0,29). Die Größe des Geschlechtschromatinkörpers, ausgedrückt in % des haploiden Genoms, betrug 7,28% (±1,18) bei XX-Weibchen und 3,26% (±0,73) bei Xx-Weibchen. Auf Grund dieser Daten wird angenommen, daß a) das Geschlechtschromatin durch das gesamte Geschlechtschromosomenmaterial, das 5% des Haploidsatzes übersteigt, gebildet wird, und b) das x-Chromosome bei den Xx-Weibchen stets an der Geschlechtschromatinbildung beteiligt ist. Die Geschlechtschromosomenreplikation ging zeitlich wie folgt vor sich: a) zu Beginn der S-Periode beginnt ein X-Chromosom früh mit der Replikation, während das andere X-Chromosom und das x- und Y-Chromosom die DNS-Synthese als letzte beginnen; b) im intermediären Stadium der S-Periode replizieren die Geschlechtschromosomen in gleicher Weise wie die Autosomen, c) in den späten und endstadien replizieren beide Geschlechtschromosomen in ihrer gesamten Ausdehnung spät. Das Muster der Chromosomenreplikation zu Beginn der S-Periode kann als aufschlußreicher für die Unterscheidung von Hetero- und Euchromatin im Geschlechtsgenom vonAkodon azarae angesehen werden als das Replikations-Muster der Endphase.
    Notes: Summary Sex chromosome length, sex chromatin area and the pattern of sex chromosome replication were determined in the field mouseAkodon azarae (Rodentia Cricetidae). Among the animals studied a group of spontaneously deleted females was included. The complemont in deleted females was 38Xx, being the x a grossly deleted X-chromosome. Length of sex chromosomes expressed as percentage of the haploid set was: X-chromosome 7.89% (±1.18), x-chromosome 1.47% (±0.20), Y-chromosome 1.15% (±0.29). Area of sex chromatin expressed as percentage of the haploid genome was 7.28% (±1.18) in XX females and 3.26% (±0.73) in Xx females. According to these data it was assumed that: (a) sex chromatin was formed by all those sex chromosome material in excess of the 5% of the haploid set; (b) the x-chromosome in Xx females was always involved in sex chromatin formation. Time-sequence of sex chromosome replication was as follows: (a) at the beginning of the S period one X-chromosome starts replication carly while the other X, the x and the Y-chromosomes are the last to initiate DNA synthesis; (b) in the intermediate stage of the S period sex chromosomes replicate in the same way as autosomes; (c) in late and final stages of the S period both sex chromosomes are late replicating in their whole extension. It is concluded that the pattern of sex chromosome replication at the beginning of the S period may be more informative than the pattern at the end of the S phase to distinguish between hetero-and euchromatin in the sex genome ofAkodon azarae.
    Type of Medium: Electronic Resource
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