What makes the cell cycle tick? a celebration of the awesome power of biochemistry and the frog egg

The cell cycle, a 19th century discovery of cytologists, only achieved a satisfactory biochemical explanation in the last 20 years of the 20th century. This personal retrospective focuses on how biochemical studies of the frog egg helped identify the cyclin-based mitotic oscillator and how this approach quickly merged with genetic studies in yeast to establish the basic mechanism of the eukaryotic cell division cycle. The key feature that made this a cyclic process was regulated protein degradation, mediated by ubiquitin, catalyzed by a massive enzyme machine, called the Anaphase Promoting Complex.