Feedback loops in the signal paths controlling gene expression.

Theoretical and empirical studies support the concepts suggesting emission of electromagnetic fields by living cells. Experiments performed in our laboratory indicate, in addition, tight links between attributes of these fields and the phase of cell division cycle, i.e., processes governed by gene transcription. This work supplements the now quite extensive literature concerning gene networks in that it identifies the well-known feedback mechanisms in exact topological and quantitative terms. Special diagrammatic apparatus is employed for this purpose. The simple system comprising one gene and one transcription factor (binding as a dimer to the gene regulatory region), controlled via phosphorylation process by external signal, is analyzed to demonstrate the approach. The diagram representative of the system's dynamics contains a feedback loop; the so-called transmission function of this feature of diagram topology is shown to control the dependences of gene product concentration on the stimulus intensity.