Chromosomal Localization of 18S-28S rDNA and (TTAGGG)n Sequences in Two South African Dormice of the Genus Graphiurus (Rodentia: Gliridae)

Classical cytogenetics and mapping of 18S-28S rDNA and (TTAGGG)n sequences by fluorescence in situ hybridization (FISH) was performed onGraphiurus platyops (GPL) andGraphiurus ocularis (GOC) metaphases with the aim to characterize the genomes. In both species, inverted DAPI karyotypes showed the same diploid number, 2n = 46, and hybridization of the (TTAGGG)n probe revealed interstitial telomeric sequences (ITSs) at the centromeres of almost all bi-armed chromosomes. FISH with the rDNA probe localized nucleolus organizer regions (NORs), at the terminal ends of the p arms of the subtelocentric pairs 16 and 17 in both species and detected additional signals on GPL8 and GOC18, 19, and 22. The species have similar karyotypes, but their chromosome pairs 18-22 differ in morphology; these are acrocentric inG. platyops, as also confirmed by C-banding, and subtelocentric inG. ocularis. These differences in pairs 18-22 were also highlighted by hybridization of the telomeric probe (TTAGGG)n, which showed the small p arms inG. ocularis enriched with ITSs. FISH of rDNA probes detected multiple NOR loci inG. ocularis, underlining the intense evolutionary dynamics related to these genes. Although theGraphiurus species analyzed have similar karyotypes, the results on the repetitive sequences indicate a complex pattern of genomic reorganization and evolution occurring in these phylogenetically close species.Cytogenet Genome Res
Source: Cytogenetic and Genome Research - Category: Genetics & Stem Cells Source Type: research