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    Differentiation of the XY Sex Chromosomes in the Fish Hoplias malabaricus (Characiformes, Erythrinidae): Unusual Accumulation of Repetitive Sequences on the X Chromosome

    Texto completo
    Autor(es):
    Cioffi, M. B. [1] ; Martins, C. [2] ; Vicari, M. R. [3] ; Rebordinos, L. [4] ; Bertollo, L. A. C. [1]
    Afiliação do(s) autor(es):
    1 Univ Fed Sao Carlos, Dept Genet Evolucao, BR-13565905 Sao Carlos, SP - Brazil
    2 Univ Estadual Paulista, Inst Biociencias, Dept Morfol, Botucatu, SP - Brazil
    3 Univ Estadual Ponta Grossa, Dept Biol Estrutural Mol Genet, Ponta Grossa - Brazil
    4 Univ Cadiz, Fac Ciencias Mar & Ambient, Genet Lab, Puerto Real - Spain
    Tipo de documento: Artigo Científico
    Fonte: SEXUAL DEVELOPMENT; v. 4, n. 3, p. 176-185, 2010.
    Citações Web of Science: 22
    Assunto(s):

    Citogenética molecular

    Cromossomos sexuais

    Cromossomo Y

    Resumo
    The wolf fish Hoplias malabaricus (Erythrinidae) presents a high karyotypic diversity, with 7 karyomorphs identified. Karyomorph A is characterized by 2n = 42 chromosomes, without morphologically differentiated sex chromosomes. Karyomorph B also has 2n = 42 chromosomes for both sexes, but differs by a distinct heteromorphic XX/XY sex chromosome system. The cytogenetic mapping of 5 classes of repetitive DNA indicated similarities between both karyomorphs and the probable derivation of the XY chromosomes from pair No. 21 of karyomorph A. These chromosomes appear to be homeologous since the distribution of (GATA)(n) sequences, 18S rDNA and 5SHindIII-DNA sites supports their potential relatedness. Our data indicate that the differentiation of the long arms of the X chromosome occurred by accumulation of heterochromatin and 18S rDNA cistrons from the ancestral homomorphic pair No. 21 present in karyomorph A. These findings are further supported by the distribution of the Cot-1 DNA fraction. In addition, while the 18S rDNA cistrons were maintained and amplified on the X chromosomes, they were lost in the Y chromosome. The X chromosome was a clearly preferred site for the accumulation of DNA repeats, representing an unusual example of an X clustering more repetitive sequences than the Y during sex chromosome differentiation in fish. Copyright (C) 2010 S. Karger AG, Basel (AU)

    Processo FAPESP: 07/05565-5 - Marcadores cromossômicos em Hoplias malabaricus (Characiformes, Erythrinidae): citogenética comparativa entre citótipos
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