What is Operon

Gene expression patterns are dependent on their internal cell environment of their DNA, their immediate internal cell environment, and the integrity of their DNA. It also depends on the cell's external environment comprised of signals from other parts of the body including chemicals, nutrients, and/or mechanical stress. Gene regulation is achieved by a wide range of mechanisms that cells use to control whether genes are transcribed, when they are transcribed, and to regulate the quantity of certain proteins based on the cellular and/or environmental feedback. Proper regulation of gene expression is required by organisms to respond to continually changing environmental conditions. Some bacterial genes are transcribed as a unit under a regulatory system called an operon which contains functionally related genes. Three well studied operons include the lactose operon, histidine operon, and tryptophan operon. Gene regulation in higher organisms can occur at various stages from DNA level to protein assembly. This chapter explores this aspect of genes.