Presence of two DNA polymerases in Tetrahymena pyriformis.

Micronuclear Ribonucleic Acid in Tetrahymena Pyriformis

The presence of RNA in the micronucleus of Tetrahymena pyriformis was detected by electron microscope radioautography after incubation with tritiated precursors. The specificity of RNA labeling was shown by ribonuclease digestion. The period of appearance of labeled RNA in the micronucleus is approximately coincident with the DNA synthesis period for the micronucleus. Pulse-chase experiments sh...

Inhibition of rRNA synthesis following incorporation of 5-bromodeoxyuridine into DNA of Tetrahymena pyriformis.

Tetrahymena pyriformis was grown on chemically defined medium in the presence of 5-bromodeoxyuridine (BUdR). Under these growth conditions more than 60% of the thymidine sites in DNA were substituted with BUdR. It was found that RNA synthesis was strongly inhibited by the presence of BUdR in DNA. To assure that incorporation of BUdR into DNA was a prerequisite of the effect observed, BUdR was a...

Replication and Functions of Macronuclear Dna in Synchronously Growing Populations of Tetrahymena Pyriformis

Deoxyribonucleic acid polymerase from Tetrahymena pyriformis. Purification and properties of the major activity in exponentially growing cells.

The major DNA polymerase activity from exponentially growing Tefrahymena pyriformis was isolated and purified approximately l&000-fold relative to the specific activity of DNA polymerase in crude extracts. The enzyme aggregates at low ionic strength. In solutions of ionic strength 0.25 M or greater, the enzyme exists as a single species with an approximate molecular weight of 80,000. DNase acti...

The Distribution of Dna among Dividing Mitochondria of Tetrahymena Pyriformis

A squash technique was developed for log phase Tetrahymena pyriformis which permitted the resolution of over 100 individual mitochondria from a single cell. Mitochondria incorporated thymidine at all stages of the cell cycle, even when nuclear DNA synthesis was not occurring. During the stage of macronuclear DNA synthesis, however, there was a significant increase in the extent of mitochondrial...