Presence of feedback mechanisms, both positive and negative, in the gene regulation systems is generally appreciated. The present study proposes a diagrammatic representation of these phenomena that affords their exact formulation and reveals some new facts. Topology of feedback relationships is defined by diagram configuration and quantitative evaluation is afforded by analytical apparatus coming with the diagrams. In particular, criterion for occurrence of bistability and synergy of positive and negative feedback are described in exact manner using the concept of transmission functions associated with diagram edges. The approach is demonstrated on genetic regulatory system comprising two genes whose transcription is controlled by activator and repressor proteins mutually competing for binding to the same responsive element of the DNA.