TWO DIFFERENT UNITS OF DNA REPLICATION AS REVEALED BY THE USE OF HYDROXYUREA IN SYNCHRONIZED L CELLS

Abstract

Application of hydroxyurea to L5 cells partially synchronized by the harvesting procedure markedly improved the degree of synchrony in the DNA synthesis phase without permitting severe unbalanced growth of cells. Using the resynchronized DNA-making cells, the two-unit replication of DNA in a single cell nucleus was revealed, the early-replicating DNA being more actively synthesized than the late-replicating DNA, as far as L5 cells are concerned. The rate of RNA and protein syntheses was not disturbed by treatment with hydroxyurea.