Compare How a Negative Repressible Control Mechanism and a Positive

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The Answer is In a negative,repressible regulatory mechanism,transcription of the structural gene(s)occurs in the absence of the co-repressor,but not in its presence.When the repressor/co-repressor complex is bound to the RPBS,it prevents RNA polymerase from transcribing the structural genes.In the absence of co-repressor,free repressor cannot bind to the RPBS; thus,RNA polymerase can bind to the promoter and transcribe the structural genes.In a positive,repressible control mechanism,the product of the regulator gene,the activator,must be bound to the RPBS in order for RNA polymerase to bind to the promoter and transcribe the structural gene(s).When co-repressor is present,it forms a complex with the activator protein,and this activator/co-repressor complex is unable to bind to the RPBS; consequently,RNA polymerase cannot bind to the promoter and transcribe the structural gene(s).

Compare How a Negative Repressible Control Mechanism and a Positive

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