CHROMOSOMAL DISTRIBUTION OF THE MAJOR SATELLITE DNA OF SOUTH-AMERICANRODENTS OF THE GENUS CTENOMYS

The chromosomal distribution of the major satellite DNA of South Ameri can rodents of the genus Ctenomys was analyzed in eight species by in situ hybridization, using a probe isolated from C. porteousi. The hybr idization patterns showed different numbers of chromosomes with positi ve pericentromeric regions and/or complete short arms. In some species , a positive signal was scarce (or not detectable, as in C. opimus), a nd was usually located in the pericentromeric areas (C. occultus and C . latro). In those species where the satellite was highly amplified, i ts chromosomal localization tended to encompass the entire length of t he short arms. These patterns were compared with C-band distribution p atterns in the same species. We discuss the putative evolutionary tren d of this satellite DNA in the genus Ctenomys and suggest that it evol ved from a strictly pericentromeric localization to comprising the who le short arms of some chromosomes.