Operon System

The class before the test, we learned about the Operon System. An operon can come in two different forms. It can be either repressible or inducible.


In a repressible operon, the repressor is initially inactive, and so the RNA Polymerase can go down the DNA strand and create a complementary mRNA strand (transcription). Then, it goes through RNA processing and through transcription and eventually becomes a protein. The protein can then act as the co-repressor, and activate the repressor.




In an inducible operon, the repressor is initially active, so the RNA Polymerase is blocked from going down the strand and eventually creating a protein from that gene. When an inducer, such as arabinose for the pGLO lab, is added, the repressor pops out of the operator and becomes inactive. The RNA Polymerase then goes down the DNA, and through Transcription, RNA Processing, and Translation, the a protein is made. This protein is an enzyme, arabinase, that eats the sugar, arabinose. When all of the sugar, inducer, is eaten up, the repressor becomes active again, and blocks off the RNA Polymerase.