Sequence homology near the center of the extrachromosomal rDNA palindrome in Tetrahymena

The nucleotide sequence in the central region of the extrachromosomal ribosomal DNA palindrome of Tetrahymena pigmentosa has been determined. The sequence data show that 26 nucleotides at the very center are not palindromic. A segment of 34 base-pairs just outside the non-palindromic region is highly conserved between Tetrahymena pigmentosa and Tetrahymena thermophila, while the rest of the central regions show little sequence homology.