Coupled positive feedback loops regulate the biological behavior

Coupled positive feedback loops are frequently-occurring motifs in gene transcription regulatory networks and signaling pathways. So it's very important to investigate the function of coupled positive feedback loops. In this paper we establish mathematical models of coupled positive feedback loops. Through the bifurcation analysis, we prove that two coupled positive feedback loops can generate reversible and irreversible switch. And coupled positive feedback loops can strengthen bistable, enlarge signal and extend the signal reaction time. Coupled positive feedback loops play an important role in regulate biological behaviors.