Alternative pathways in the processing of ribosomal RNA precursor in Drosophila melanogaster

The size of RNA molecules that are intermediates in the processing of ribosomal RNA in Drosophila melanogaster has been determined by gel electrophoresis under fully denaturing conditions. These molecules have been characterized by transfer from agarose gels to diazobenzyloxymethyl-paper and hybridization with restriction fragments derived from cloned ribosomal DNA. Five cleavage sites leading to the production of 18 S and 28 S RNA have been mapped in the precursor. The first cleavage in the precursor molecule occurs at one of two different sites. Therefore, we propose two alternative pathways for the processing of D. melanogaster ribosomal RNA. A precursor molecule to 2 S and 5.8 S ribosomal RNA has been identified in nuclear RNA.