Cell cycle variants and their control during Drosophila development

For developmental biology, the most relevant aspect of the cell cycle is presumably the fact that it is not really a perfect cycle. By going from one to two cells, the cycle does not end exactly where it started, but it contributes building blocks for the construction of multicellular organisms. Entry into, progression through, and exit from the cell cycle are controlled during development in order to generate sufficient cells in the correct spatial and temporal pattern. G1- and G2-cyclin-dependent kinases, which govern the progression through the cell cycle, are expected therefore to be regulated by developmental inputs. Analyses in Drosophila have revealed a variety of mechanisms that control the activity of these kinase complexes in different cell cycle types at successive developmental stages.