Purification of tDNA from yeast.

tRNA-tDNA hybrids from yeast have been isolated. The main step in purification was chromatography on a BD-cellulose column with salt gradients and formamide, which separates the hybrid material from excess DNA. The hybrids were characterized by density centrifugation in CS2SO4 and by treatment with alkali and pancreatic ribonuclease. Experiments in which DNA that had been sheared to different molecular weights was used for hybrid formation suggest that the tRNA cistrons are tandemly arranged and that the external spacer DNA is preserved in the tDNA.