Figure 10-2. Jacob and Monod model of transcriptional regulation of the lac operon by lac repressor.

Figure 10-2Jacob and Monod model of transcriptional regulation of the lac operon by lac repressor

When lac repressor binds to a DNA sequence called the operator (O), which lies just upstream of the lacZ gene, transcription of the operon by RNA polymerase is blocked. Binding of lactose to the repressor causes a conformational change in the repressor, so that it no longer binds to the operator. RNA polymerase then is free to bind to the promoter (P) and initiate transcription of the lac genes; the resulting polycistronic mRNA is translated into the encoded proteins. [Adapted from A. J. F. Griffiths et al., 1993, An Introduction to Genetic Analysis,5th ed., W. H. Freeman and Co.]

From: Section 10.1, Bacterial Gene Control: The Jacob-Monod Model

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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