Question

Describe the intracellular events that occur when a population of wild type ( lac+) escherichia coliis transferred from a medium with glucose as the sole nutrient source to a medium with lactose as the sole nutrient source.

Answer 1

The lac repressor protein is bound to the operator region of the lac operon when there is no lactose in the medium. When introduced in lactose, it binds to an allosteric site on the repressor causing its to change conformation and release from the operator. This allows the polymerase that is bound to the promoter region to proceed transcription of the lac operon genes (LacZ, Lac A, and Lac Y). Translation of these genes forms enzymes that enable the organism to break down lactose for energy.