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Operons [https://en.wikipedia.org/wiki/Operon] are a critical genetic component of most prokaryotic cells. There are many different operons that are responsible for the production of proteins with a wide range of functions, the most well-known of which are the Lac and Trp operons, responsible for producing enzymes which metabolize lactose and tryptophan respectively. Despite many differences in each operon and the proteins that they encode, operons all function in the same general manner. Structurally, each operon contains a regulator, an operator, and one or more structural genes. The regulator protein is responsible for managing the expression level of the structural genes, the operator is similar to a promoter in a regular gene and is where transcription begins, and the structural genes code for proteins. The regulator protein (produced as a result of expression of the regulator gene) most often acts in a repressive manner, though this is not always the case. That is, the regulator protein will bind to the operator of the operon, inhibiting the binding and/or progression of RNA polymerase[http://proteopedia.org/wiki/index.php/RNA_polymerase] to the structural genes, thus inhibiting transcription of the genes into mRNA.  If the regulator protein were to consistently be active, there could never be adequate expression of the structural genes, so there must be a way to inactive the regulator protein, thus enabling expression of the structural genes. This is achieved through the binding of an inhibitor to the regulator protein. Since regulator proteins are DNA binding proteins, often this inhibition is allosteric rather than competitive, that is the inhibitor is not something that mimics DNA and binds to the active site physically blocking DNA from binding. Rather, the inhibitor of the regulator binds to somewhere other than the active site of the protein, changing it in some way which decreases the proteins affinity or ability to bind DNA. The Chromosome Determined Zinc Responsible (Czr) operon acts in exactly this manner, Czr A specifically is the regulator protein. The role of Czr A in the Czr operon is described in further detail under biological function.