In confirmation of earlier results, nucleoside diphosphokinase is shown to be a ‘step’ enzyme in Schizosaccharomyces pombe with a sharp doubling in activity at the beginning of the cell cycle. These doubling steps occur at the same time in the cycle in the smaller cells of the mutant wee1.6. An important result is that the activity steps persist with normal cell cycle timing after a block to the DNA-division cycle imposed by the cycle mutants cdc2.33 and cdc2.33wee1.6. This is clear proof that oscillatory controls of some cell cycle events can persist after the main periodic events of the DNA-division cycle have been abolished.

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