A paper by Joe Culotti and Lee Hartwell had a major impact on me when I first read it as a PhD student in 1972 and was thinking about what to do next in my scientific life. It was one of a series of papers from Lee Hartwell’s lab that showed how genetics could be used to analyse the developmental sequence that makes up the eukaryotic cell cycle. I was already interested in the cell cycle as a fundamental developmental programme common to all cells but was struggling to work out how to investigate this critical biological process. It was Lee’s series of papers that showed me the way.

Examination of the nuclear cytology in the mutants revealed that the blocks occurred at different stages of mitosis: some prior to nuclear elongation, others when the nucleus was elongated, and yet others when the nucleus had divided into two but still connected by a thread. Finally, synchronous cultures demonstrated that completion of mitosis was required for the subsequent round of DNA synthesis, indicating that different cell cycle events were dependent upon one another.