Genetic regulatory circuits (also referred to as transcriptional regulatory circuits) is a concept that evolved from the Operon Model discovered by François Jacob and Jacques Monod.  They are functional clusters of genes that impact each other's expression through inducible transcription factors and cis-regulatory elements.
Genetic regulatory circuits are analogous in many ways to electronic circuits in how they use signal inputs and outputs to determine gene regulation. Like electronic circuits, their organization determines their efficiency, and this has been demonstrated in circuits working in series to have a greater sensitivity of gene regulation. They also use inputs such as trans and cis sequence regulators of genes, and outputs such as gene expression level. Depending on the type of circuit, they respond constantly to outside signals, such as sugars and hormone levels, that determine how the circuit will return to its fixed point or periodic equilibrium state. Genetic regulatory circuits also have an ability to be evolutionarily rewired without the loss of the original transcriptional output level. This rewiring is defined by the change in regulatory-target gene interactions, while there is still conservation of regulatory factors and target genes.