The relationship between the cell cycle and control of development has been studied by a genetic analysis of Caulobacter crescentus. The behavior of conditional cell division mutants showed that cell cycle events, such as DNA replication and cell division, are organized into a dependent pathway(s), i.e., later steps cannot preceed until earlier ones are completed. The ability of these strains to develop normally under nonpermissive conditions suggested that flagellin synthesis and stalk formation are dependent on the completion of different cell-cycle steps: the periodicity of flagellin synthesis is achieved by coupling it to either DNA chain elongation or completion, and stalk formation is dependent on a later step in the cell-division pathway. These developmental events are not themselves required for cell division, however.