HIGH-RESOLUTION FLUORESCENCE IN-SITU HYBRIDIZATION OF RBM-RELATED ANDTSPY-RELATED COSMIDS ON RELEASED Y CHROMATIN IN HUMANS AND PYGMY CHIMPANZEES

Applying two-colour fluorescence in situ hybridization (FISH) we simul taneously hybridized RBM- and TSPY-related cosmids to Y chromosomes in prophase and to released Y chromatin in interphase nuclei of man and pygmy chimpanzee. Whereas, even on prophasic Y chromosomes, no resolut ion of the overlapping RBM and TSPY signal clusters could be achieved, the RBM and TSPY signals are completely separated from each other in our maximum released Y chromatin stretches in interphase nuclei. These results unequivocally lend support to the view that the RBM and TSPY families have an interspersed organization on the Y chromosomes of man and higher apes. Thus, the distribution of RBM and TSPY signals might well go back to a common organization of these genes next to each oth er on an ancient Y chromosome.