The *E.coli* trp operon codes for five genes required for tryptophan synthesis. When tryptophan in the cell is low, the trp operon is expressed. When tryptophan levels are sufficient, the operon is repressed. The trp repressor binds directly with tryptophan which causes a conformational change in the repressor that allows it to bind the operator sequence and repress transcription.

University of Wisconsin - Madison

Repressible operons typically code for proteins needed to make products required for cellular pathways. When the cell requires the product of this operon, this operon will be expressed. But once the product is accumulated in the cell, it binds the repressor of the operon and the operon is repressed or turned off. This regulates the amount of products in the cell through gene regulation and expression. 

Repressible Operons

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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