rDNA molecules from Tetrahymena macronuclei. Upper panel: Electron micrograph of individual rDNA molecules from Tetrahymena macronuclei. Shown are two linear molecules, each ∼22 kb in length. Lower panel: Map of the deduced structure of 22-kb rDNA molecules showing the CCCCAA/GGGGTT telomeric repeats at both ends. Reproduced from Gall (2009), Fig. 13 a (upper panel) and Fig. 14 (lower panel).