Complete sequence of the extrachromosomal rDNA molecule from the ciliate Tetrahymena thermophila strain B1868VII.

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.