Restriction enzyme digestion of heterochromatin in Drosophila nasuta.

ABSTRACT

In situ digestion of metaphase and polytene chromosomes and of interphase nuclei in different cell types of Drosophila nasuta with restriction enzymes revealed that enzymes like AluI, EcoRI, HaeIII, Sau3a and SinI did not affect Giemsa-stainability of heterochromatin while that of euchromatin was significantly reduced; TaqI and SalI digested both heterochromatin and euchromatin in mitotic chromosomes. Digestion of genomic DNA with AluI, EcoRI, HaeIII, Sau3a and KpnI left a 23 kb DNA band undigested in agarose gels while with TaqI, no such undigested band was seen. The AluI resistant 23 kb DNA hybridized in situ specifically with the heterochromatic chromocentre. It appears that the digestibility of heterochromatin region in genome of Drosophila nasuta with the tested restriction enzymes is dependent on the availability of their recognition sites.