Navegando por Palavras-chave "constitutive heterochromatin"
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- ItemSomente MetadadadosChromosome mapping of 28S ribosomal genes in 11 species of Cassidinae (Coleoptera: Chrysomelidae)(Czech Acad Sci, Inst Entomology, 2017) Lopes, Amalia T.; Fernandes, Flavia R.; Schneider, Marielle C. [UNIFESP]In this study, we examined for the first time the distribution of the 28S ribosomal genes in beetles of the subfamily Cassidinae. More than 55% of the species in this subfamily have a similar karyotype, 2n = 16 + Xy(p). For this work, we selected species belonging to the tribes Cassidini and Mesomphaliini, which have, respectively, the most conserved and diversified karyotype characteristics within the Cassidinae. An analysis of 11 species revealed that rDNA sites on one pair of autosomes is the most frequent pattern, occurring in 10 species. This condition occurs in the seven genera examined and in species of both of the tribes, Cassidini and Mesomphaliini. Nevertheless, the differences in the locations of 28S rDNA were more pronounced in the tribe Cassidini and among species with similar karyotype characteristics. On the other hand, in Mesomphaliini, the increase in the diploid number was not accompanied by an increase in the number of ribosomal sites. Moreover, the comparison of the number and localization of major rDNA sites with the distribution of constitutive heterochromatin indicates that there is no direct correlation between the dispersion of constitutive heterochromatin and 28S rDNA genes in Cassidinae.
- ItemSomente MetadadadosComparative cytogenetic analysis among filistatid spiders (Araneomorphae: Haplogynae)(Amer Arachnological Soc, 2017) Paula-Neto, Emygdio; Cella, Doralice Maria; Araujo, Douglas; Brescovit, Antonio Domingos; Schneider, Marielle Cristina [UNIFESP]The family Filistatidae is considered sister to Synspermiata or sister to Hypochilidae. Cytogenetic knowledge of this family could be useful for understanding the mechanism of chromosome evolution that has occurred within the group. In this work, two filistatid species belonging to distinct subfamilies, Kukulcania hibernalis (Hentz, 1842) (Filistatinae) and Misionella mendensis (Mello-Leitao, 1920) (Prithinae), were investigated using standard and differential chromosome staining. Analysis of mitotic and meiotic cells revealed the diploid 2n male = 25 for K. hibernalis and 2n male = 21 for M. mendensis. Both species exhibited a sex chromosome system of the X1X2Y type and metacentric/submetacentric chromosomes. In prophase I cells, the sex chromosomes were in a trivalent configuration with all elements associated without chiasma through their terminal regions. Both species revealed six nucleolar organizer regions on the terminal region of three autosomal pairs. In K. hibernalis, constitutive heterochromatin was located mainly in the terminal regions of autosomes and sex chromosomes while in M. mendensis, the heterochromatin occurred in the pericentromeric region of all chromosomes. Despite the scarcity of cytogenetic information for Filistatidae, the available results show the occurrence of high variability in the diploid number but with the maintenance of the X1X2Y sex chromosome system. Additionally, the karyotype differentiation in the species of this family seems to have involved not only the number of autosomes but also specific chromosomal sites, such as the constitutive heterochromatic regions.
- ItemSomente MetadadadosDifferential chromosome sensitivity to 5-azacytidine in Alzheimer's disease(Karger, 1998-09-01) Payão, Spencer Luiz Marques [UNIFESP]; Smith, M. D.; Bertolucci, Paulo Henrique Ferreira [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Background: The methylation process in the DNA has been considered a control mechanism of gene activity, connected with genetic imprinting. 5-Azacytidine (5-AZC) is known to be a demethylation agent. Objective: We studied the cytogenetic effect of 5-AZC in Alzheimer's disease patients and in two control groups. Methods: Peripheral lymphocyte cultures derived from 8 patients with Alzheimer's disease and 8 elderly and 8 healthy young individuals, all female, were studied. The parameters investigated were: the undercondensation of constitutive heterochromatin of chromosomes 1, 9, and 16: the number of lesions in fragile sites 1q42 and 19q13; heterochromatin association, and the total number of induced lesions. Results: Our results showed a significantly increased frequency of undercondensation of chromosomes 1, 9, and 16 in Alzheimer's disease patients when compared with elderly and young healthy groups. Conclusion: These results suggest that the demethylating action of 5-AZC could reveal differential gene activity in the Alzheimer group at the level of cellular division.
- ItemSomente MetadadadosLocation of 45S Ribosomal Genes in Mitotic and Meiotic Chromosomes of Buthid Scorpions(Zoological Soc Japan, 2014-09-01) Mattos, Viviane Fagundes; Carvalho, Leonardo Sousa; Cella, Doralice Maria; Schneider, Marielle Cristina [UNIFESP]; Univ Estadual Paulista; Univ Fed Piaui; Universidade Federal de Minas Gerais (UFMG); Universidade Federal de São Paulo (UNIFESP)Buthid scorpions exhibit a high variability in diploid number within genera and even within species. Cytogenetically, Buthidae differs from other families of Scorpiones based on its low diploid numbers, holocentric chromosomes, and complex chromosomal chains, which form during meiosis. in this study, we analyzed the distribution of the 45S ribosomal DNA (rDNA) genes in the mitotic and meiotic chromosomes of seven buthid species belonging to the genera Rhopalurus and Tityus with the ultimate goal of elucidating the chromosome organization in these scorpions. the chromosome number ranged from 2n = 6 to 2n = 28. Despite the high variance in diploid number, all species examined carried their 45S rDNA sites in the terminal region of exactly two chromosomes. Analyses of meiotic cells revealed 45S rDNA clusters in the chromosomal chains of Rhopalurus agamemnon, Tityus bahiensis, Tityus confluens, and Tityus martinpaechi, or in bivalent-like configuration in Rhopalurus rochai, Tityus bahiensis, Tityus confluens, Tityus fasciolatus, and Tityus paraguayensis. in the species examined, the 45S rDNA sites colocalized with constitutive heterochromatin regions. in light of the high chromosome variability and maintenance of number and terminal position of 45S rDNA sites in buthids, the heterochromatin may act to conserve the integrity of the ribosomal genes.