a.) Propose an explanation for why transcription is not occurring in diagram A,

Question

a.) Propose an explanation for why transcription is not occurring in diagram A, but is occurring in diagram B.

b.) Propose an explanation for why RNA polymerase is not bound to the promoter in diagram A of Model 3.

Model 3-Positive Control of a Gene Terminato Diagram A Regulatory Promoter Operator Gene DNA ne mRNA 3' RNA polymerase Activator protein Diagram B Regulatory Promoter Operator Terminator Gene DNA ene ene ene RNA polymerase 3' Ligand (messenger molecule) 5' mRNA Inactive activator protein Active activator protein Protein Al Protein YProtein L

Explanation / Answer

A) Transcription is not occuring in diagram A due to the fact that the activator protein that is needed for the transcription to initiate is inactivated in diagram A in the absence of its ligand.

Now, in diagram B, as soon as ligand appears, it binds itself with the inactivated activator protein and activates it. This activated protein go abd bind to the promoter region and now create a site for polymerase to sit which was not able to sit on promoter before. Once the polymerase sits on the promoter region, it begins transcription and mRNA and protein for Gene X,Y and Z are generated.

B) Rna polymerase does not bind to the promoter region in model A because it reequires an additional protein (Activator protein) to get attached to promoter properly before initiating transcription.

Thank you.

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