Class 12th Biology 2017 Set2 Outside Delhi Board Paper Solution
Explain how a polycistronic structural gene is regulated by a common promoter and a combination of regulatory genes in a lac-operon
Lac-operon consist of one regulatory gene 'i' which codes for the repressor protein promoter (P) and operator (O) are adjecent to gene.
Structural genes z, y, a code for enzymes (β-galactosidase, peruecase and transacetylase respectively)
The regulator gene i-synthesize the repressor protein, in absence of inducer, the repressor protien binds the operotor region of the operon, prevents transcription.
The repressor is inactivated in the presence of an inducer that binds with it, this allows RNA polymerase access to promoter and transcription proceeds.
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