Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance3 Marks
Question
Explain the role of lactose in ‘Lac Operon’.
✓
Answer
A small amount of beta-galactoside permease enzyme is present in cell even when Lac operon is switched off and it allows a few molecules of lactose to enter into the cell.
Lactose binds to repressor and inactivates it.
Repressor – lactose complex cannot bind with the operator gene, which is then turned on.
RNA polymerase transcribes all the structural genes to produce lac m-RNA which is then translated to produce all enzymes.
Thus, lactose acts as an inducer.
When the inducer level falls, the operator is blocked again by repressor and structural genes are repressed again. This is negative feedback.
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