IPTG is a molecule with a structure much like lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by ββ-galactosidase. Predict what would occur to lac operon regulation if IPTG were added to E. coli growth medium containing no glucose or lactose.

Verified step by step guidance

1. Understand the role of IPTG: IPTG mimics lactose and can bind to the lac repressor, causing the repressor to change shape and release from the lac operon. This allows transcription of the operon's genes.
2. Recognize the function of the lac operon: The lac operon includes genes that code for proteins necessary for the uptake and metabolism of lactose in E. coli. Key components include the lacZ gene (coding for β-galactosidase), lacY (coding for galactoside permease), and lacA (coding for a thiogalactoside transacetylase).
3. Predict the effect of IPTG: Since IPTG can bind to the lac repressor but is not a substrate for β-galactosidase, it will not be metabolized. Binding of IPTG to the lac repressor will inactivate the repressor, leading to continuous expression of the lac operon.
4. Consider the absence of glucose: In the absence of glucose, cAMP levels are high, which leads to the activation of CAP (catabolite activator protein). CAP binds to the promoter of the lac operon, enhancing RNA polymerase binding and transcription.
5. Conclude the outcome: With IPTG present and no glucose, the lac operon will be highly active, leading to high levels of transcription of lacZ, lacY, and lacA. This results in increased production of β-galactosidase, galactoside permease, and thiogalactoside transacetylase, even though there is no lactose to metabolize.