Contrast the role of the repressor in an inducible system and in a repressible system.

Video transcript

Hi everyone. Welcome back. Here's our next problem. It says the lack operation has turned on when a low lactose finds duty. So what I would call that the lack opera as an inducer operation. So it's a default setting is off and that occurs because the lack of repressor is bound to the operator. And when that's the case, the opera, the lac repressor protein is blocking the promoter site where RNA polymerase comes in and binds to start transcription of those black jeans. So our lac repressor is bound to the operator to have that setting off. So the black opera will be turned on when a low lactose binds to this lac repressor protein, causing it to release from the operator so that it will no longer be blocking the promoter. That allows RNA polymerase to come in and start transcribing the lack jeans. So are correct answer. Here is choice be repressor. You want these genes to be turned off when there's lactose absent because if there's no lactose around, why do you want to be spending energy transcribing the genes to digest lactose. So when lactose is present, some of it gets I summarized into a low lactose and some of that allow lactose binds to the lac repressor protein that causes it to come off allows that transcription to take place. So when we look at our other answer choices. Choice A is operator operators not warily lactose binds operators where the lac repressor is bound. So that's why it's not correct choices, promoter promoter is where the RNA polymerase spines, it's what's blocked by the lac repressor but not where the A. Lacto spines, too. So it's not our answer. And then finally, choice the opera on while the AL Actos does not buy into any site on the operation itself. The lactose binds to the lac repressor, which is bound to the operator within the opera. So opera is not our correct choice either. So again, the lack opera has turned on. When Allah lactose binds to the choice be repressor. See you in the next video.