Sex chromosomes evolved independently during evolution of the vertebrate group, in a way that their pattern of evolution succeeds differently from the autosomal chromosomes. Regarding fish there is great diversity of sex chromosome systems, presenting both homomorphic and heteromorphic sex chromosomes throughout the group. In heteromorphic sex chromosomes, in one of the homologs, Y or the W, it may occur a vast presence of heterochromatin, rich in repetitive sequences. One example of these sequences, the satellite DNA class, may be related to the evolutionary process of sex chromosomes differentiation due to their highly dynamic characteristics. The genus Megaleporinus is an interesting model for the study of sex chromosomes evolution in fish, due to some of its species presenting female heterogamety (ZZ/ZW), with an elevated rate of repetitive sequences in their heteromorphic sex chromosomes. The function and organization of these repetitive sequences in the sex chromosomes of fish is not yet known, therefore, this project has the objective to study the genomic organization and possible evolutionary history of M. elongatus sex chromosomes through satellite DNA sequences isolation, amplification and probe hybridization in of both sexes of the species.
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