5. An illustration of the architectural organization of lac operon, a biological

Question

5. An illustration of the architectural organization of lac operon, a biological control system is illustrated below. Use this diagram as an aid to answer the question(0- lac repressor gene; Z, Y, A - lac operon structural genes; P lac promoter; O lac operator) ?? ? a) Aresearcher wanted to switch on the system permanently, so that he wants to sell out the products of Z, Yand A. What he does is he cultures bacteria in the absence of sucrose and in presence of his magical compound nick named as "YJKLMN". Come out with a logical reasoning regarding the mechanism of action of YJKLMN, so that in its presence the operon is always on b) The researcher adds 500 copies of the gene P. Is it going to affect the operon in any way? c) If the region O is removed from the gene cluster, what will happen to the operon?

Explanation / Answer

a. The compund YJKLMN acts as an inducer. It binds to the repressor protein , alters its conformational status such that they are not able to bind to operator region of lac operon. Thus RNA polymerase is free to transcribe the target genes by binding to the promotor region of lac operon.

b. If 500 copies of gene is added, it will lead to more transcription of the target gene leading to a stronger operon region.

c. If O is removed from the gene cluster, no transcription takes place as this is the place where RNA polymerase binds and transcribes the target genes. O is a gene cluster comprising of genes for Z,Y and A each coding for a particular enzyme.

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