According to the lac−operon concept, which functional unit of the bacterial genetic material is responsible for suppressing the activity of the operator gene in the absence of lactose?
According to the lac−operon concept, which functional unit of the bacterial genetic material is responsible for suppressing the activity of the operator gene in the absence of lactose?
The correct option is C Regulator gene
The promoter is a DNA segment that serves to initiate transcription of a gene by providing the binding site for RNA polymerase. They are present upstream near the transcription start sites of genes. Thus, option D is incorrect. The gene that codes for any RNA / protein product which does not serve as regulatory protein is known as structural genes. The lac z, lac y and lac a genes in lac operon are the structural genes; option A is incorrect. Regulator gene regulates the expression of structural genes by its protein products that are mostly transcription factors. The transcription factors encoded by regulator proteins are also called as the repressors, thus repressor is the product of regulator gene, not a part of operon which makes option C incorrect. In the absence of lactose, the repressor binds to the operator region which is located just upstream the binding site of the RNA polymerase and hence prevents the binding and transcription. Therefore, regulator gene suppresses the activity of operator via repressor. Option B is correct.
The promoter is a DNA segment that serves to initiate transcription of a gene by providing the binding site for RNA polymerase. They are present upstream near the transcription start sites of genes. Thus, option D is incorrect. The gene that codes for any RNA / protein product which does not serve as regulatory protein is known as structural genes. The lac z, lac y and lac a genes in lac operon are the structural genes; option A is incorrect. Regulator gene regulates the expression of structural genes by its protein products that are mostly transcription factors. The transcription factors encoded by regulator proteins are also called as the repressors, thus repressor is the product of regulator gene, not a part of operon which makes option C incorrect. In the absence of lactose, the repressor binds to the operator region which is located just upstream the binding site of the RNA polymerase and hence prevents the binding and transcription. Therefore, regulator gene suppresses the activity of operator via repressor. Option B is correct.
