A number of mutations affect the expression of the lactose operon in E. coli: I^

Question

A number of mutations affect the expression of the lactose operon in E. coli: I^- a mutant lac repressor that cannot bind the lac operator I^s a mutant lac repressor that cannot bind lactose O^C a mutant lac operator that cannot bind repressor Lacl P^- a mutant lac promoter that cannot bind RNA polymerase Z^- a mutant lac Z lost beta-galactosidase activity Y^- a mutant permease that cannot g transport lactose into the cell Consider the following strains each with the indicated mutations in the lac operon. Predict the levels of Beta- galactosidase activity (either high or low) under two growth conditions: with lactose absent or present. Please assume that no glucose is present.

Explanation / Answer

In above all the case, except 9th and 10th lactose is present. In the absence of inducer, lac repressor block all but very few level of transcription of genes take place. when cell are deficient in lactose, permease allow uptake off beta-galactosidase catalysis conversion of lactose to allolactose, acting as inducer which further binds to the repressor.This all ring conformational change of reprressor symetry and allow RNA polymerase to function.

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