  A feedback mechanism that involves the proteins p53 and mdm2, induces cell
death as a controled response to severe DNA damage. A minimal model for this
mechanism demonstrates that the respone may be dynamic and connected with the
time needed to translate the mdm2 protein. The response takes place if the
dissociation constant k between p53 and mdm2 varies from its normal value.
Although it is widely believed that it is an increase in k that triggers the
response, we show that the experimental behaviour is better described by a
decrease in the dissociation constant. The response is quite robust upon
changes in the parameters of the system, as required by any control mechanism,
except for few weak points, which could be connected with the onset of cancer.
