15. Operon System

  Today in class we learned about the operon system. The operon system only exists in the prokaryotic cells (bacteria), and there are only two types of operons - repressible (on to off) and inducible (off to on).
  One example of the repressible type of operon systems is tryptophan. A regulatory gene is synthesized into an inactive repressor protein while the RNA polymerase transcribes the rest of the genes to create tryptophan. Once enough tryptophan is created, the tryptophan will connect to the repressor protein and switch it to be active. the active repressor will bond with the operator that started the transcription, and eventually RNA polymerase stops creating more tryptophan.
  The second type of operon system is inducible, and one example for that would be lactose. The repressor protein synthesized in this system is active at the beginning. And once enough lactose is created, the lactose will connect enter the repressor protein and triggers to be inactive. The repressor protein will leave the operator and allow lactase to be synthesized to reduce the amount of lactose in the body.

- Andy Liu '15