Chromosomal organization of repetitive DNA sequences in Astyanax bockmanni (Teleostei, Characiformes): dispersive location, association and co-localization in the genome

Repetitive DNA sequences constitute a great portion of the genome of eukaryotes and are considered key components to comprehend evolutionary mechanisms and karyotypic differentiation. Aiming to contribute to the knowledge of chromosome structure and organization of some repetitive DNA classes in the fish genome, chromosomes of two allopatric populations of Astyanax bockmanni were analyzed using classic cytogenetics techniques and fluorescent in situ hybridization, with probes for ribosomal DNA sequences, histone DNA and transposable elements. These Astyanax populations showed the same diploid number (2n = 50), however with differences in chromosome morphology, distribution of constitutive heterochromatin, and location of 18S rDNA and retroelement Rex3 sites. In contrast, sites for 5S rDNA and H1, H3 and H4 histones showed to be co-located and highly conserved. Our results indicate that dispersion and variability of 18S rDNA and heterochromatin sites are not associated with macro rearrangements in the chromosome structure of these populations. Similarly, distinct evolutionary mechanisms would act upon histone genes and 5S rDNA, contributing to chromosomal association and co-location of these sequences. Data obtained indicate that distinct mechanisms drive the spreading of repetitive DNAs in the genome of A. bockmanni. Also, mobile elements may account for the polymorphism of the major rDNA sites and heterochromatin in this genus. © 2013 Springer Science+Business Media Dordrecht.

Programas de la Organización de Estados Americanos relacionados con la urbanización en América Latina = Programmes of the Organization of American States connected with urbanization in Latin America

Los documentos del Seminario fueron publicados por UNESCO en 1961 con el título: La urbanización en América Latina/Urbanization in Latin America

General outlines of the Organization of a Civil Registration Service in Latin America (English summary)

Organized by the United Nations, through its Statistical Office, the Bureau of Technical Assistance Operations, the Economic Commission for Latin America and the Latin American Demographic Centre, in co-operation with the Government of Peru, the Inter-American Statistical Institute, the Inter-American Children's Institute, the Pan American Health Organization and the Inter-American Civil Registration Association