Replicon size and rate of DNA replication in the macronucleus of Tetrahymena pyriformis
Andreeva, L.F.; Andreeva, T.F.; Merkulova, N.A.; Borkhsenius, S.N.
Tsitologiia 21(3): 318-326
1979
ISSN/ISBN: 0041-3771 PMID: 107637 Document Number: 140112
The size of replication units (or replicons) measured in T. pyriformis strain GL macronuclear DNA reaches 20-30 .mu.m, according to DNA fiber autoradiography and alkaline isokinetic sucrose gradient centrifugation. The synthesis of new DNA-fragments (replicons) and their subsequent assembly are separated by time intervals (30 min). The rate of A synthesis for 1 fork averaged 0.6-0.7 .mu.m/min. These data were obtained for cells of cultures being both in the expotential phase of growth and those synchronized by starvation-refeeding. The generation time of T. pyriformis cells, calculated by the increase of the part of labeled nuclei, is almost 2 h; the synthesis lasts 1 h. The total amount of replication units in polyploid (polygenomic) T. pyriformis macronucleus is about 3000. Their initiation during S-period is presumably asynchronous.