In this video, we're going to introduce inducible operons. Inducible operons are operons that are normally turned off, and when they are turned off, the genes will not be expressed. However, they can be turned on under very specific conditions, and when they can be turned on, that means that they can be induced. The conditions where they can be turned on include the presence of what's known as an inducer, which we'll introduce here very shortly.
What happens is an active repressor protein represses transcription under normal conditions. The inducible operon will be normally turned off when there is an active repressor protein repressing transcription. However, the active repressor protein can be inactivated by the inducer molecule. The inducer molecule will bind to the active repressor protein and inactivate the repressor, which will allow for transcription to proceed. In other words, the inducer molecule inactivates the repressor protein, and when it inactivates the repressor protein, transcription will be turned on. This is why it's called an inducible operon because it can be induced even though it's normally turned off.
If we take a look at our image down below, we can get a better understanding of an inducible operon in the presence of an inducer molecule. We're showing you the inducible operon, which is aligned with positive gene regulation because, as we discussed in our previous lesson videos, positive gene regulation occurs when you turn a gene on. Here on the left-hand side, the inducible operon under normal condition is shown as turned off because an active repressor protein will bind to the operator and block or prevent transcription, and so none of the genes will be expressed normally. However, under very specific conditions that include the presence of an inducer molecule, the inducer molecule will bind to the repressor and cause the repressor to change its shape, changing its conformation. The inactive repressor here can no longer bind to the operator, meaning that the operator is going to be free, and the RNA polymerase is capable of binding to the promoter and proceeding with transcription.
In the presence of an inducer molecule, the inducible operon can be turned on. You can see here we have our light switch being flipped into the on state. When transcription is turned on, the mRNA will be made, and the proteins will follow with translation. The products here are being made. Inducible operons undergo positive gene regulation, which means that they can be turned on, although they're normally off.
This concludes our brief introduction to inducible operons, and as we move forward, we'll continue to learn more about operons and get some practice. So, I'll see you all in our next video.