title: Molecular cytogenetic characterization of the Amazon River dolphin Inia geoffrensis.
abstract: Classical and molecular cytogenetic (18S rDNA, telomeric sequence, and LINE-1 retrotransposon probes) studies were carried out to contribute to an understanding of the organization of repeated DNA elements in the Amazon River dolphin (boto, Inia geoffrensis). Twenty-seven specimens were examined, each presenting 2n = 44 chromosomes, the karyotype formula 12m + 14sm + 6st + 10t + XX/XY, and fundamental number (FN) = 74. C-positive heterochromatin was observed in terminal and interstitial positions, with the occurrence of polymorphism. Interstitial telomeric sequences were not observed. The nucleolar organizer region (NOR) was located at a single site on a smallest autosomal pair. LINE-1 was preferentially distributed in the euchromatin regions, with the greatest accumulation on the X chromosome. Although the karyotype structure in cetaceans is considered to be conserved, the boto karyotype demonstrated significant variations in its formula, heterochromatin distribution, and the location of the NOR compared to other cetacean species. These results contribute to knowledge of the chromosome organization in boto and to a better understanding of karyoevolution in cetaceans.
authors.affiliation: Programa de Pós-Graduação em Genética, Conservação e Biologia Evolutiva, Laboratório de Genética Animal, Instituto Nacional de Pesquisas da Amazônia, Av André Araújo, 2936 Petrópolis, Manaus, AM 69083-000, Brazil. heidi_bio@yahoo.com.br
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Bonifácio
authors.forename: Vera M F
authors.initials: VM
authors.lastname: da Silva
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Martin
authors.forename: Eliana
authors.initials: E
authors.lastname: Feldberg
mesh_terms: D000818:Animals; D003582:Cytogenetics; D004275:DNA, Ribosomal / Q000235:genetics; D004289:Dolphins / Q000235:genetics*; D022041:Euchromatin / Q000235:genetics / Q000378:metabolism; D007621:Karyotyping; D009697:Nucleolus Organizer Region / Q000235:genetics; D045483:Rivers
chemical_list: D004275:DNA, Ribosomal; D022041:Euchromatin