Does the presence of glucose affects the ability of lactose to induce ß-gal?

Expert Solution

Answer-

1. When glucose is present then synthesis of beta galactosidase decreases as glucose is used as energy source and lactose is utilized in very small amounts.

2. To the upstream of lac promoter, CAP binding site present which binds to catabolite activator protein (CAP) when cyclic AMP (cAMP) is present. In cell, cAMP is produced in large amounts in absence of glucose. So that, when glucose is absent, CAP-cAMP binds to CAP site which helps to RNA polymerase to bind promoter and gene of beta galactosidase is expressed. Beta galactosidase then utilizes lactose.

3. When glucose enters the cell, firstly it inhibits lactose permease so that lactose can not enter cell and also glucose cannot exit the cell. In presence of lactose cAMP can not be synthesized and when cAMP is absent, it can not bind to CAP and CAP can not bind to CAP binding site. In absence of CAP, RNA polymerase cannot bind to promoter and beta galactosidase gene is not expressed.

4. So that presence of glucose affects the ability of lactose to induce beta galactosidase by decreasing expression of beta galactosidase.

gladiator answered 2 years ago

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