CYTOGENETIC AND MOLECULAR ANALYSIS OF THE SATELLITE DNA OF THE GENUS CTENOMYS (RODENTIA OCTODONTIDAE) FROM URUGUAY

The genus of subterranean rodents Ctenomys presents the widest range o f variability in diploid number among mammals (from 2n = 10 to 2n = 70 ). In Uruguay, this variability is observed in karyotypes with 2n = 44 , 50 or 58 and two geographically isolated populations with 70 chromos omes but different karyotypic structure. The last three populations we re analyzed in the present study. They present a satellite DNA, which was isolated from genomic DNA after AluI digestion. In situ hybridizat ion showed that this satellite DNA is located in the centromeric regio n of a few chromosomes, coincident with Hoechst 33258 staining and C-b anding patterns. A similar satellite DNA was detected in Argentinian s pecies of this genus. We established that, in spite of differences in number of positive heterochromatic blocks per karyotype, the C value i s the same in the three populations studied. The nature and possible e volutionary path of this repeated DNA is discussed.