  Specific activator and repressor transcription factors which bind to specific
regulator DNA sequences, play an important role in gene activity control.
Interactions between genes coding such transcription factors should explain the
different stable or sometimes oscillatory gene activities characteristic for
different tissues. Starting with the model P53-MDM2 described into [6] and the
process described into [5] we developed a new model of this interaction.
Choosing the delay as a bifurcation parameter we study the direction and
stability of the bifurcating periodic solutions. Some numerical examples are
finally given for justifying the theoretical results.
