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1.
Cytogenet Genome Res ; 160(3): 148-155, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32272470

RESUMO

Transposable elements have driven genome evolution and plasticity in many ways across a range of organisms. Different types of biotic and abiotic stresses can stimulate the expression or transposition of these mobile elements. Here, we cytogenetically analyzed natural fish populations of the same species living under different environmental conditions to test the influence and organization of transposable elements in their genome. Differential behavior was observed for the markers Rex 1, Rex 3, and Rex 6 in the chromosomes of individuals of the same species but coming from different environments (polluted and unpolluted). An increase in the number of Rex transposable elements in the chromosomes and their influence on the genome of populations living in a polluted environment indicates that they must be under constant adaptive evolution.


Assuntos
Adaptação Fisiológica/genética , Elementos de DNA Transponíveis/genética , Evolução Molecular , Peixes/genética , Animais , Cromossomos/genética , Genoma/genética , Rios , Estresse Fisiológico/genética
2.
Cytogenet Genome Res ; 160(1): 29-37, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32092757

RESUMO

The fish family Cynodontidae belongs to the superfamily Curimatoidea, together with the Hemiodontidae, Serrasalmidae, Parodontidae, Prochilodontidae, Chilodontidae, Curimatidae, and Anostomidae. The majority of the species of this superfamily that have been analyzed to date have a diploid chromosome number of 2n = 54. Differentiated sex chromosomes (with female heterogamety) have been observed only in the Prochilodontidae, Parodontidae, and Anostomidae. The present study provides the first description of differentiated sex chromosomes in the cynodontid species Cynodon gibbus, which has a ZZ/ZW system, and shows that repetitive DNA has played a fundamental role in the differentiation of these sex chromosomes.


Assuntos
Caraciformes/genética , Cromossomos Sexuais , Animais , Bandeamento Cromossômico , DNA , Evolução Molecular , Feminino , Heterocromatina/química , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Hibridização de Ácido Nucleico , Sequências Repetitivas de Ácido Nucleico
3.
Cytogenet Genome Res ; 2018 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-30025386

RESUMO

The chromosomes of 2 flea beetle species from central Amazonia, Omophoita abbreviata and O. aequinoctialis (Alticini), were investigated through analysis of meiotic and mitotic cells. These species belong to the subtribe Oedionychina, a taxon that has unique cytogenetic features, such as giant sex chromosomes which are aligned at a distance during meiosis I (asynaptic). O. abbreviata and O. aequinoctialis have a meiotic formula of 10II + X + y, which is predominant in this subtribe. While the species of the genus Omophoita possess a relatively stable karyotype, a typical feature for Oedionychina, the present study identified inter- and intrapopulational variation in chromosome morphology, constitutive heterochromatin, and the presence and number of B chromosomes in O. aequinoctialis. In addition, FISH mapping of telomeric sequences revealed signals in the collochores, raising several questions on the chromosomal evolution in this group.

4.
Cytogenet Genome Res ; 153(2): 96-104, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29186711

RESUMO

The genus Colomesus is the sole representative of the family Tetraodontidae in the Amazon region. Here, Colomesus asellus was analyzed using conventional and molecular cytogenetic protocols. Its diploid chromosome number is 2n = 46 with 12 meta-, 10 submeta-, 16 subtelo-, and 8 acrocentric chromosomes and a fundamental number of FN = 84. An XX/XY sex chromosome system was identified. Mapping of 18S rDNA correlated with the nucleolus organizer regions (Ag-NORs) in the short arms of the 2 X chromosomes in females and in the Y chromosome in males. C-banding revealed heterochromatin in the centromeric regions of all chromosomes, except for pair 3. Prominent sex chromosome-specific heterochromatin amplification was observed, covering the short arms of the Y chromosome almost entirely. FISH with telomeric and tropomyosin (tpm1) sequences, respectively, revealed terminal signals in all chromosomes. The analysis of extended DNA fibers confirmed the colocalization and the interspersed pattern of the telomeric and tpm1 sequences. Thus, this study highlights the remarkable evolutionary dynamism presented by the Amazonian puffer fish regarding the differentiation of a heteromorphic XY sex chromosome system and a particular sex-specific amplification of rDNA sites. This is the first record of such an association in the Tetraodontidae family.


Assuntos
Cromossomos Sexuais/genética , Processos de Determinação Sexual , Tetraodontiformes/genética , Animais , Antígenos Nucleares/genética , Brasil , Bandeamento Cromossômico , DNA Ribossômico/genética , Feminino , Amplificação de Genes , Hibridização in Situ Fluorescente , Masculino , RNA Ribossômico 18S/genética , Sequências Repetitivas de Ácido Nucleico , Telômero/genética , Telômero/ultraestrutura , Tropomiosina/genética
5.
Comp Cytogenet ; 9(4): 465-81, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26752156

RESUMO

The structure and organization of repetitive elements in fish genomes are still relatively poorly understood, although most of these elements are believed to be located in heterochromatic regions. Repetitive elements are considered essential in evolutionary processes as hotspots for mutations and chromosomal rearrangements, among other functions - thus providing new genomic alternatives and regulatory sites for gene expression. The present study sought to characterize repetitive DNA sequences in the genomes of Semaprochilodus insignis (Jardine & Schomburgk, 1841) and Semaprochilodus taeniurus (Valenciennes, 1817) and identify regions of conserved syntenic blocks in this genome fraction of three species of Prochilodontidae (Semaprochilodus insignis, Semaprochilodus taeniurus, and Prochilodus lineatus (Valenciennes, 1836) by cross-FISH using Cot-1 DNA (renaturation kinetics) probes. We found that the repetitive fractions of the genomes of Semaprochilodus insignis and Semaprochilodus taeniurus have significant amounts of conserved syntenic blocks in hybridization sites, but with low degrees of similarity between them and the genome of Prochilodus lineatus, especially in relation to B chromosomes. The cloning and sequencing of the repetitive genomic elements of Semaprochilodus insignis and Semaprochilodus taeniurus using Cot-1 DNA identified 48 fragments that displayed high similarity with repetitive sequences deposited in public DNA databases and classified as microsatellites, transposons, and retrotransposons. The repetitive fractions of the Semaprochilodus insignis and Semaprochilodus taeniurus genomes exhibited high degrees of conserved syntenic blocks in terms of both the structures and locations of hybridization sites, but a low degree of similarity with the syntenic blocks of the Prochilodus lineatus genome. Future comparative analyses of other prochilodontidae species will be needed to advance our understanding of the organization and evolution of the genomes in this group of fish.

6.
Cytogenet Genome Res ; 147(2-3): 161-8, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26867142

RESUMO

Repetitive DNA is the largest fraction of the eukaryote genome and comprises tandem and dispersed sequences. It presents variations in relation to its composition, number of copies, distribution, dynamics, and genome organization, and participates in the evolutionary diversification of different vertebrate species. Repetitive sequences are usually located in the heterochromatin of centromeric and telomeric regions of chromosomes, contributing to chromosomal structures. Therefore, the aim of this study was to physically map repetitive DNA sequences (5S rDNA, telomeric sequences, tropomyosin gene 1, and retroelements Rex1 and SINE) of mitotic chromosomes of Amazonian species of teiids (Ameiva ameiva, Cnemidophorus sp. 1, Kentropyx calcarata, Kentropyx pelviceps, and Tupinambis teguixin) to understand their genome organization and karyotype evolution. The mapping of repetitive sequences revealed a distinct pattern in Cnemidophorus sp. 1, whereas the other species showed all sequences interspersed in the heterochromatic region. Physical mapping of the tropomyosin 1 gene was performed for the first time in lizards and showed that in addition to being functional, this gene has a structural function similar to the mapped repetitive elements as it is located preferentially in centromeric regions and termini of chromosomes.


Assuntos
Mapeamento Cromossômico/métodos , Genoma/genética , Lagartos/genética , Sequências Repetitivas de Ácido Nucleico/genética , Animais , Brasil , Evolução Molecular , Geografia , Heterocromatina/genética , Hibridização in Situ Fluorescente , Lagartos/classificação , RNA Ribossômico 5S/genética , Retroelementos/genética , Especificidade da Espécie , Tropomiosina/genética
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