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Contributions to the understanding of the origin and evolution of the vertebrate sex chromosomes, based on the repetitive DNAs study.


Although most of fish and amphibians species do not have differentiated sex chromosomes, there is a great diversity concerning the mechanisms of chromosomal sex determination including heterogametic females or males and single or multiple systems. In most cases, a difference between the sex partners involves heterochromatic blocks and this fact is very well established in ZZ/ZW systems in which loss or gain of heterochromatin are the main causes of differentiation between these chromosomes. One of the fish species to be studied in the present study, belonging to the Leporinus group (ZZ/ZW) has already been the subject of studies in our laboratory, in which interesting results have been obtained, mainly in relation to repetitive sequences. Despite the information already obtained, little is known about the evolution of sex chromosomes and sex determination in the Leporinus group and in fish. The species of amphibian, Proceratophrys boiei, to be studied in the present project presents a supposed system of sex chromosomes also of the ZZ/ZW type, that has not yet been studied from the molecular point of view involving the isolation of repetitive sequences. Thus, in this project we intend to map the repetitive sequences, mainly those of the satellites type, present in the genome of these two species of vertebrates, verifying the relation of them with the sex chromosomes. In addition, it is also intended to study other repetitive sequences, which may not be associated with sex chromosomes, but may show interesting chromosomal markers for both groups of vertebrates. All the probes will be hybridized in the chromosomes of the mentioned species and the results compared between species and between different populations in order to know specific species/population markers. The data obtained may provide valuable information for the understanding of the structural organization and evolution of the genome of fish and amphibians. (AU)

Articles published in Pesquisa FAPESP Magazine about the research grant:
Los misterios de ser macho o hembra 
Male or female? The mystery unfolds 
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