CBSE 2025 · Region 6 · Set 1 · Q25 · 3 marks
Explain how the addition of lactose in the medium regulates the switching on of the lac operon in bacteria.
Marking-scheme solution
Lactose transported into the cell through permease, in the presence of an inducer lactose the repressor is inactivated by interaction with the inducer, this allows RNA polymerase access to the promoter and transcription proceeds
Molecular Basis of InheritanceRegulation of Gene ExpressionUnderstandshort_answermedium
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CBSE Class 12 Biology past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.