RESUMO
Modern mole voles of the genus Ellobius are characterized by species-specific features of autosomes and sex chromosomes. Owing to the use of the Zoo-FISH method, the nomenclature of chromosomes was refined and nonhomologous Robertsonian translocations indistinguishable by G-staining were identified for Ellobius tancrei, which is a species with a wide chromosome variation of the Robertsonian type. The electron-microscopic analysis of synaptonemal complexes in F1 hybrids of forms with 2n = 50 and 2n = 48 revealed the formation of a closed SC-pentavalent composed of three metacentrics with monobrachial homology and two acrocentrics. Segregation of chromosomes of such complex systems is impeded by disturbances in the nucleus architecture leding to the formation of unbalanced gametes and to a dramatic reduction in fertility of hybrids. Our data support the hypothesis that the formation of monobrachial homologous metacentric chromosomes can be considered as a way of chromosomal speciation.
Assuntos
Arvicolinae/genética , Cromossomos de Mamíferos/genética , Translocação Genética , Animais , Cromossomos de Mamíferos/ultraestrutura , Hibridização in Situ FluorescenteRESUMO
Fluorochrome-labeled oligonucleotides (n = 44) corresponding to mouse genome repetitive sequences were hybridized in situ with pachytene nuclei of mouse spermatocytes. Signals of the repetitive sequences MaLR, MER, and (GT)22 were found to be dispersed through chromatin, and signals of BI 1 repeats and minisatellites were mostly attached to synaptonemal complexes immunostained with anti-SYCP3 antibodies. These results suggest that B 1 repeats and minisatellites are candidates for sequences anchoring chromatin to synaptonemal complexes.
