Allolactose induces the synthesis of the enzyme lactase. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose)as a potential food source. Which of the following occurs when the lactose enters the cell?
A)The repressor protein attaches to the regulator.
B)Allolactose binds to the repressor protein.
C)Allolactose binds to the regulator gene.
D)The repressor protein and allolactose bind to RNA polymerase.
E)RNA polymerase attaches to the regulator.

Question

Quizplus · Accepted Answer

When lactose (containing allolactose) enters the cell, allolactose binds to the repressor protein, causing it to undergo a conformational change and detach from the operator region. This allows RNA polymerase to bind to the promoter region and transcribe the genes responsible for lactose metabolism, including the lactase enzyme. The regulator gene codes for the repressor protein, so allolactose does not directly bind to it. The repressor protein and allolactose do not bind to RNA polymerase together. The repressor protein does not attach to the regulator in response to lactose.

Allolactose Induces the Synthesis of the Enzyme Lactase