Operon System and pGLO Lab

There are two kinds of operon systems, repressible and inducible. I am going to explain inducible because it is the same kind of operon system used in the pGLO lab.

In an inducible operon system it begins off and we have to turn it on. First, the promoter attracts RNA polymerase since the operator already has a repressor(protein) the RNA polymerase is not able to read genes anymore. For example, arabinose(sugar) would come from an outside system like agar and go into the repressor to inactivate it. Once the operator is open, the RNA polymerase is no longer locked and can continue to read genes. When RNA polymerase is reading genes it creates arabinose (enzyme) which can digest the arabinose. Once all the arabinose is all digested the protein/ repressor goes back into the operator and is locked again. The operon system only uses necessary energy, not extra.

In the pGLO lab, the bacteria (E. coli) transformed with pGLO will not glow in two weeks because in order for it to glow all the time there must be a constant supply of arabinose. But after two weeks the supply of arabinose will decrease and the bacteria will not be able to glow. Through GFP/ arabinose operon system, if arabinose is no longer supplied the repressor will go back into the operator and the RNA polymerase will no longer be able to read the GFP (green fluorescent protein) gene, and will not fluoresce anymore.