Regulation, regulation, regulation: we might strive for our personal freedom, but — certainly at the biological level — we are continually being watched and controlled.

Such biological surveillance is exemplified by the many checkpoint pathways that operate during the cell cycle. In the DNA synthesis (S) phase, DNA must be accurately replicated so that, when the cell divides, each daughter cell receives an exact copy of the original genome. Any problems that have arisen during DNA duplication, and any other replication-independent genome damage, should be amended before mitosis. On page 792, Jiri Bartek, Claudia Lukas and Jiri Lukas review the checkpoints that operate in S phase to prevent the transmission of defective DNA to daughter cells.

As Fátima Gebauer and Matthias Hentze discuss on page 827, the translation of mRNA is also tightly regulated, and the participation of small micro RNAs in this regulation has renewed interest in this mechanism of gene control.

After mRNA translation, nascent polypeptides must be properly folded to generate native cellular proteins with intricate tertiary structures. On page 781, Jason Young, Vishwas R. Agashe, Katja Siegers and F. Ulrich Hartl introduce us to the aptly named molecular chaperones, which ensure that the folding of these protein 'debutants' proceeds without mishap.

Finally, on page 805, David Hipfner and Stephen Cohen discuss the complex mechanisms that maintain the balance between cell proliferation and cell death — pathways that are crucial for normal tissue growth during embryonic development. In the fly, the contest between cells for survival signals is an important component of these regulatory mechanisms and, as the authors point out, it is likely that future research will uncover a similar role for cell competition in the control of vertebrate development.