Topographical analysis of yeast ribosomal DNA by cleavage with restriction endonucleases

Yeast ribosomal DNA (rDNA) was digested with the restriction enzymes Hind III, Hind II and a mixture of Hind II and Hind III. The cleavage products were analyzed by electrophoresis on 1.5% agarose gels. Several distinct bands could be observed, which are derived from the redundant ribosomal transcription units. They are superimposed on a rather broad smear of background DNA, representing the heterogenous 'spacer' sequences. From the restriction maps, together with data obtained by partial digestion, a physical map for the ribosomal transcription unit in yeast could be constructed.