OPERON MODEL OF GENE EXPRESSION When lactose is present, a small amount of it enters the cell and is converted to allolactose. Allolactose acts as an inducer. It binds to the repressor protein and alters it so that it cannot bind to the operator site. RNA polymerase can now transcribe the structural genes into mRNA, and the enzymes are made. Lactose is said to induce enzyme synthesis, and the lac operon is called an inducible operon. Repressible operons work almost the same, but this time the structural genes are constantly transcribed unless they are turned off (repressed). Genes for the enzymes involved in the
This is the end of the preview. Sign up
access the rest of the document.