Fig. 4B: An Inducible Operon in the Absence of an Inducer
(The Lactose Operon of Escherichia coli)

Step 3: With the active repressor protein bound to the Operator region, RNA polymerase (the enzyme responsible for the transcription of genes) is unable to bind to the Promoter region of the operon.
Step 4: If RNA polymerase does not bind to the Promoter region, the 3 lac operon structural genes (lacZ, lac Y, and lacA) are not transcribed into mRNA.
Step 5: Without the transcription of these genes, the enzymes needed for the utilization of the sugar lactose by the bacterium are not synthesized.

Illustration of An Inducible Operon in the Absence of an Inducer (The Lactose Operon of Escherichia coli).jpg by Gary E. Kaiser, Ph.D.
Professor of Microbiology, The Community College of Baltimore County, Catonsville Campus
This work is licensed under a Creative Commons Attribution 4.0 International License.
Based on a work at https://cwoer.ccbcmd.edu/science/microbiology/index_gos.html.

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Last updated: September, 2018
Please send comments and inquiries to Dr. Gary Kaiser