Question

Why is lacZ required for lacY induction by lactose, but not IPTG? A. Because LacZ is...

Why is lacZ required for lacY induction by lactose, but not IPTG?

A. Because LacZ is a transcriptional regulator of lacY.

B. Because LacZ produces allo-lactose required for induction.

C. None of the answers are correct

. D. Because LacZ produces cAMP required for induction.

E. Because LacZ allosterically inactivates the LacI repressor.

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Answer #1

even if the inducer is absent the lac operon is expressed at very-very low levels, so beta-galactosidase and permease is produced in the cell at very low concentrations, permease helps in the lactose uptake, this lactose is converted to allolactose by beta-galactosidase, allolactose binds to the lac repressor and prevents its binding to lac operator, so lac operon can be expressed at higher levels, so induction by lactose requires lacZ.

B) Because LacZ produces allo-lactose required for induction.

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