This year the world has celebrated the 50th anniversary of the discovery of DNA's structure (see, for example, Nature 421, 395–453; 2003). Meanwhile, however, another important scientific anniversary is in danger of slipping past unmarked.

Also in 1953, Alma Howard and Stephen Pelc published their work on cell proliferation in bean (Vicia faba L.) roots1. They grew plants with a 32P isotope label and showed that it was incorporated into DNA in the nucleus only during interphase, and that it took 12 hours from the end of division until the beginning of the isotope uptake into new DNA. By analysing heterogeneous populations of meristematic cells, Howard and Pelc deduced that DNA synthesis takes about six hours, and that cells enter prophase of the next mitosis only eight hours after DNA synthesis is completed.

Howard and Pelc were the first to ascribe a timeframe to cellular life and they proposed the existence of four periods in the cell cycle: a period of cell division, the pre-S-phase (called G1), the S-phase (a period of DNA synthesis) and period G2, or the pre-mitotic period. The concept of the cell cycle was born.

Since then, cell-cycle studies have flourished. It is unfortunate, therefore, that this discovery is now almost forgotten (though not totally: see The view of the cell cycle formed a basis for determining time parameters of the cell cycle (by labelling mitoses and other methods) and for the biochemical and molecular events that take place at each stage of the life of the cell between divisions in various groups of organisms.

As we know, the concept was later developed and the checkpoints in cell-cycle regulation and universal control mechanisms were determined by using genetics and molecular biology2.

All these recent achievements stemmed from Howard and Pelc's study — which calls for another 50-year anniversary celebration to be held by the international scientific community.