Leland Hartwell

Leland Hartwell used baker's yeast, Saccharomyces cerevisiae, as a model system for genetic studies of the cell cycle. In an elegant series of experiments 1970-71, he isolated yeast cells, in which genes controlling the cell cycle were altered (mutated). By this approach, he identified genes specifically involved in cell cycle control, so called CDC-genes (cell division cycle genes). One of these genes, designated CDC28, controls the first step in the progression through the G1-phase of the cell cycle (the function "start"). Hartwell also identified the fundamental role of "checkpoints" in cell cycle control. These checkpoints monitor that all steps in the previous phase have been correctly executed and ensure a correct order between the cell cycle phases.