46. The graph below depicts diauxic growth by Escherichia coli in a medium conta

Question

46. The graph below depicts diauxic growth by Escherichia coli in a medium containing lactose and glucose. Illustrate on the following diagrams the state of the lac operon and its the culture in time A and time B. What would be the state of the operon and its regulators if coli was grown in a medium with only glucose as a carbon source (C)? regulators for the E All glucose consumed Lactose used Glucose Lag time Time Control region Structural genes DNA Regulatory Promoter Operator Control region Structural genes DNA Regulatory Promoter Operator Operon Control region Structural genes DNA Regulatory Promoter Operator gene

Explanation / Answer

A. Lac operon will be inactive as glucose is present. cAMP-CAP complex ensures that operon is functional only when glucose is absent.

B. Lac operon will be active. In the presence of lactose, lacI repressor is bound by lactose and hence can not occupy the operator. So, RNA pol can actively transcribe the structural genes.

C. Lac operon is inactive in the presence of glucose.

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