LONGITUDINAL DIFFERENTIATION OF CHROMOSOMES OF ASELLUS-AQUATICUS (CRUST. ISOP.) BY IN-SITU NICK TRANSLATION USING RESTRICTION ENZYMES AND DNASE-I

Asellus aquaticus is an isopod crustacean whose chromosomes cannot be differentiated by G- or R-banding techniques. In this work, we have ob tained a longitudinal differentiation of these chromosomes by in situ nick translation using restriction enzymes (HaeIII, DraI and BamHI) an d DNase I digestions. The four nucleases, with different efficiencies, have produced similar labelling patterns. Staining with DAPI, Giemsa and chromomycin A(3) reveals that the DNA of the nick-translated regio ns is generally more resistant to extraction from the chromosome. The results obtained on the heteromorphic sex chromosome pair observed in about a quarter of the males of a natural population allow several hyp otheses to be advanced on the nature and origin of chromosome dimorphi sm.