Class 12th Biology 2017 Set3 Outside Delhi Board Paper Solution
Question 24
Absence of lactose in the culture medium affects the expression of a Lac-operon in E. coli. Why and how ? Explain.
Answer
1. Lactose acts as inducer thus absence of lactose switches off the operon
2. Repressor protein produced by regulatory gene (i-gene ) is free (in the absence of inducer )
3. Repressor protein binds with the operator gene (o-gene ) ,
4. Preventing RNA polymerase to transcribe the structural gene and operon is switched off
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