According to the operon theory, the function of the regulator gene is to..?

a. code for a repressor protein that can bind to an operator


b. code for enzymes in a metabolic pathway


c. bind to the RNA polymerase molecule


d. act as RNA splicing enzymes

According to the operon theory, the function of the regulator gene is to..?
The answer is A.





An operon is a set of genes that do something. For example, the set of enzymes that let a bacteria use lactose as a carbon source: lacZ, which breaks down lactose, lacY, which lets lactose into the cell, and Lac A. The operator is a sequence of DNA just upstream of the genes in the operator. Since a cell doesn't want to use lactose as a carbon source unless there is lactose and there is no glucose, a regulator called the lac repressor binds to the operator and keeps the operon shut off. If lactose is present in the cell, it will bind to the repressor, causing it to change shape and fall off of the operator so the genes in the operator can be transcribed. (For the genes to be transcribed, glucose also has to be low, but this is regulated by a different mechanism).