MITOCHONDRIAL DNA IN TETRAHYMENA PYRIFORMIS

Contrary to the reports in the literature, no satellite DNA bands were found in DNA isolated from Tetrahymena pyriformis strains 6III, HSM, ST, or GL; all of the DNA from a given strain had a single buoyant density in CsCl. A technique for resolving 2 DNAs of only slightly different buoyant density using 2 different radioactive labels is described. Mitochondrial DNA was isolated from contamination-free mitochondria and shown to have a density identical to that of whole cell DNA. The molecular weight of this mitochondrial DNA as isolated was 30-40 × 106 daltons. Attempts to demonstrate that the mitochondrial DNA existed as a twisted circle were unsuccessful. However, the relative utilization of 3H-BUdR and 14C-TdR in the synthesis of mitochondrial DNA was shown to be different from their utilization in nuclear DNA synthesis. This provides another means for distinguishing between different DNA components in the same cell when different replication systems are involved. © 1969.