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Neo-XY body: an analysis of XY1Y2 meiotic behavior in Carollia (Chiroptera, Phyllostomidae) by chromosome painting

Classical and molecular cytogenetic analyses of mitotic and meiotic cells were performed on two species of Carollia from the family Phyllostomidae (Chiroptera), which have an XX/XY1Y2 sex determination system. Our results show that the species Carollia perspicillata and Carollia brevicauda have the same Xq-autosome translocation (neo-X). Using multicolor FISH we observed different levels of condensation of the original X and Y chromosomes when compared to the translocated autosomal segment, a likely consequence of the nucleolar organizer region blocking spreading of inactivation to the autosomal region of the neo-X. The use of chromosome painting showed the behavior of the sex chromosome trivalent – here called the ‘neo-XY body’ – in meiosis. We compared the variation between the condensation of the original X and Y and the autosome-sex chromosome axis and described the pairing between the original X-Y segments (pseudoautosomal region) and the XY2 homologous segments, suggesting genetic activity of the latter during meiosis.