Identify similarities and differences between an inducible ope...

Question

Identify similarities and differences between an inducible operon and a repressible operon in terms of

The presence and action of allosteric regulatory molecules.

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. What is the role of allosteric regulatory molecules in both inducible and repressible operon? The answer options are a to stop repressor proteins from binding B to bind with regulatory proteins and modulate their activity C to activate amino acids during translation and D to bind to specific sites on the DNA. So immediately we can eliminate option C. Now, amino acids are not activated. Remember they are brought to the ribosome via trn a steering translation. So option C is incorrect. Now, what are allosteric regulatory molecules recall that they are molecules that can reversibly bind to proteins, changing the protein's confirmation and function. Now, what role do allosteric regulatory molecules have for both inducible and repressible operon? Let's go ahead and take a look at two classic examples of OPERON to answer this question, the lack operon and the trip to pan operon on the screen. I am putting up a drawing of the lac operon. Now this shows the order of the operon going from the five prime end, then the promoter, the operator and the rest of the lac operon genes. Now recall that the lack OPERON is an inducible offer on which means it's normally turned off. However, in the presence of lactose allo lactose, which is represented by the orange circle binds to the repressor, which is represented by the blue oval. Now this causes the repressor to release from the operator site and transcription can occur. So we have alo lactose as an inducer. Now let's go ahead and talk about the trip to fan operan on the screen. I am putting up a drawing of the trip to fan operon. This OPERON has order five prime, the promoter, the operator, the rest of the trip to jeans and then the three prime end. Now recall that the Tritoon opera operon. Excuse me, let me say that again. Recall that the Trip Toan operon is a repressible operon and this means that it is usually turned on. Now, when Tritoon is present in the cell and Tritoon is represented by the green circle, it will bind to the repressor which is represented by the purple oval. What this does is it blocks transcription from occurring because now this complex, the corepressor and repressor can bind to our operator. So Trip Toan is the corepressor. Now, in these two operon, what are the allosteric regulatory molecules? It's the alo lactose and the trip to now option a or answer option A states that they both stop repressor proteins from binding. So this is true of the lac operon. The alo lactose binds to the repressor and it prevents the repressor from binding the operator. But this is not true for the Tritoon operon. So we can eliminate option A and neither alo lactose or crypto bind to specific sites on DNA. So, option D is also incorrect. The correct answer is option B to bind with regulatory proteins and modulate their activity. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

Identify similarities and differences between an inducible operon and a repressible operon in terms of
The presence and action of allosteric regulatory molecules.

Key Concepts

Operons

Inducible Operons

Repressible Operons

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