Abstract
The recent development of rDNA vectors for transformation of Tetrahymena combined with improved microinjection technology should lead to a renewed Interest in this organism. In particular, the rDNA itself constitutes an attractive system for biochemical studies. The rDNA is amplified to a level of 2% of the total DNA and exists as extrachromosomal molecules. Furthermore, the rDNA is homogeneous in sequence because It is derived from a single gene during sexual reorganization. In order to facilitate studies of this molecule, we report here a compilation of previously published sequence information together with new sequence data that completes the entire sequence of the 21 kb rDNA molecule.