16. Regulation of Expression
Review of the Lac Operon & Trp Operon
Review of the Lac Operon & Trp Operon
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in this video, we're going to do a review of the lack and trip operandi as we complete the table that you see down below. And so notice in this table. This column right here is focusing on the lack Opteron, and this column over here is focusing on the trip operandi. And so, in terms of the operation Type recalled that the lack opera is an induced herbal opera, and that is because it is normally turned off. But it can be turned on. It can be induced, and so this would be the on state, and over here this would be the off state, so it's normally or initially off, but it can be induced. It can be turned on now. The trip operandi over here recall, is a repress a ble opera, which recall means that it is normally turned on, but it can be turned off. It can be repressed. And so, uh, that is why the trip opera is a repressive. All operas now, in terms of the number of genes, recall that the lack opera has three genes which are lack Z lack y and lack A and the trip operas recall in terms of the number of genes. It has five genes which are going to be tripped A, B, C, D and E. Now, in terms of the functions of the genes within the opera on the functions of the three genes within the lack opera are to metabolize lactose or, in other words, to break down lactose in order to get energy out of lactose. And the functions of the five genes and the trip opera are to synthesize trip to fan the amino acid trip to fan synthesizer build trip to fans. Now recall that the repressor gene and the lack opera is lack. Hi and the Repressor gene and the trip opera is Trip are now the regulatory molecule, and the lack opera is a derivative of lactose, You could say a lactose derivative, Um, and for those of you that may need to know this, it is called al Oh lactose, and it acts as an inducer molecule to help induce transcription of the opera. Now, the trip, uh, operations regulatory molecule is actually trip to fan itself. And so trip to fan is going to act as a co repressor to help activate the trip. Are repressor protein. And so that takes us to the effect of the regulatory molecule. Recall that in the lack opera lactose is going to bind to the active lack. I repressor and inactivate the lack I repress er and so we have, uh the effect is in activates the repressor protein. So it starts off with an active repressor that will repress transcription. And then upon the lactose derivative binding, uh, it inactive in activates the repressor. So we have an inactive repressor over here. But when we take a look at the effect of the regulatory molecule and the trip opera on trip to fan is actually going to activate the repressor protein and so notice that the repressor protein starts off in an inactive state. But upon trip to fan binding, the repressor ends up in an active state. And so you can see these are basically opposite effects, and that's why one of them is induced herbal opera and the other one is a repressive ble opera. Now, when the regulatory molecule is absent, when the lactose derivative or this inducer is absent, of course, that means that it is going to repress er black eye is going to be in its active state. That means they will repress transcription, and the operation will be turned off in the absence of lactose. But in the absence of the regulatory molecule in the trip operas in the absence of trip to Fan, what happens is, uh, the repressor protein trip are is going to remain inactive, and that means that it will not be able to repress transcription. And that means that the opera and will be turned on without Triple Fan. And then, of course, looking at the regulatory molecule when it is present. When lactose is present, that's going to help turn on the trip Oberon. And so you can see here that, uh, in the presence of lactose uh, it is going to inactivate the repressor. It will no longer be able to repress transcription, and so transcription will be able to proceed and the opera and will be turned on. Whereas in the case of the trip opera, when trip to fan is present, it is going to activate the trip are repressor and that allows it to repress transcription. And so the opera and will then be turned off. And so basically what you can see here is that the induce herbal, the lack opera and the trip opera are practically opposites in many of these different categories. And this table here helps to be able to do a side by side comparison of these two operations. And so now that we've completed this table, we've completed our review of the lack and trip operas, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
Which of the following statements is FALSE?
The lac operon is an inducible operon that is normally turned off.
The trp operon is a repressible operon that is normally turned on.
Lactose is the inducer molecule for the lac operon.
Tryptophan is the activator molecule for the trp operon.
All of the above are true.
Which of the following statements is TRUE?
Lac I is the inducer molecule for the lac operon.
Tryptophan is an inducer molecule for the trp operon.
In the presence of lactose, the lac operon is expressed.
In the presence of tryptophan, the trp operon is expressed.