The book further describes the phenomenon of noise, and discusses how noise plays a crucial role in gene expression and the quorum sensing circuit operationusing a set of tools like frequency domain analysis, power spectral density, stochastic simulation and the whitening effect. It also explores various aspects of synthetic biology (related to bacterial communication), such as genetic toggle switch, bistable gene regulatory networks, transcriptional repressor systems, pattern formation, synthetic cooperation, predator-prey synthetic systems, dynamical quorum sensing, synchronized quorum of genetic clocks, role of noise in synthetic biology, the Turing test and stochastic Turing test.