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The CRISPR/Cas system represents an adaptive immune system found in archaea and bacteria. Various organisms possess diverse CRISPR systems, and one of the most studied and widely used is the type II CRISPR system discovered in Streptococcus pyogenes. This system uses the Cas9 nuclease in complex with a guide RNA to target a specific DNA sequence.

Further study and understanding of its mechanisms have enabled the optimization of the CRISPR/Cas9 system not only for genome editing but also for regulating gene expression by activating or repressing transcription, modifying the epigenetic profile of chromatin at various loci, visualizing the dynamics of genomic loci, and designing genetic networks. Although CRISPR/Cas systems demonstrate tremendous potential for both medicine and fundamental research, their application is limited by the presence of off-target effects.

However, using the system as transcriptional factors, which are elements of genetic networks, requires the use of a catalytically inactive version of the Cas9 protein, called dCas9. These proteins are even less specific because their mechanism of complex formation lacks the nuclease activation step, which is essentially the primary mechanism for off-target binding verification. This is a significant limitation for the rational design of genetic circuits, which requires precise values of the interaction parameters of dCas9 complexes with DNA.

Thus, the development of methods for analyzing the physicochemical parameters of dCas9-DNA interactions, investigating issues of non-specific activity, and creating improved genetic elements with enhanced specificity are key aspects for the future design of complex synthetic genetic circuits.