operon

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operon A set of adjacent structural genes whose messenger-RNA is synthesized in one piece, together with the adjacent regulatory genes that affect the transcription of the structural genes. The operon is under the control of an operator gene, lying at one end of it. Operons are concerned in the control of gene transcription leading to the formation of particular enzymes used in metabolic pathways. To date they have been found only in prokaryotes (e.g. Escherichia coli), but a number of homologous systems exist in lower eukaryotes such as fungi.

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