Final answer:
The lac repressor is inactivated when it binds to allolactose, which alters its shape and prevents it from binding to the operator DNA, allowing transcription to proceed.
Step-by-step explanation:
The lac repressor is inactivated by binding to allolactose.
The Lac operon is a segment of DNA used by a bacterium such as Escherichia coli. In its repressed state, when the bacterium is utilizing glucose as a source of carbon, the lac operon is off
To activate the operon and utilize lactose instead, lactose in the cell is converted to allolactose by the enzyme beta-galactosidase. Allolactose serves as an inducer molecule, binding to the repressor and changing its shape so that it no longer binds to the operator DNA. This allows RNA polymerase to move through the operator region and begin transcription of the lac structural genes.