What effect will each of the following have on induction of the lac operon by la

Question

What effect will each of the following have on induction of thelac operon by lactose in a medium that lacks glucose?

a. A mutation that inactivates beta-galactosidase.
b. A mutation that inactivates galactoside permease.
c. A mutation that makes the lac repressor proteinincapable of binding to the lac operator site.
d. A mutation that makes the lac operator site incapableof binding the lac repressor protein.
e. A mutation that makes the lac repressor proteinincapable of binding allolactose.

What effect will each of the following have on induction of thetrp operon by lactose?

- A mutation in the trpR gene?

-A mutation in the trpO gene?

- A mutation in the trpL gene?

Explanation / Answer

      When glucose is lacking inthe medium, the organism depends on lactose for energy.       For this lac operon comesto play.       The enzyme-galactosidase of lac operon cleaves lactose to itsindividual sugars of galactose and glucose by which the       organism will be able tosurvive.       a). When there is amutation that inactivates -galactosidase, lactose is not cleaved to glucose andgalactose due to             whichthe survival of the organism becomes difficult.       b). Galactosidepermease helps in the transport of lactose across the membrane.When there is a mutation in this             enzyme,the transportation of thelactose is inhibited.       c). lac repressorgene synthesizes a repressor protein which binds to theoperator and inhibits the expression of the            genesthat are responsible for lac operon.           Whenthere is a mutation which makes lac repressor protein incapable to bind to the operator region, the genes            responsiblefor lac operon are expressed continuously.         d). When the lacoperator site is incapable of binding to the repressor protein,there won't be anyregulation and the lac           operon genes areexpressed.       e). Allolactose is aninducer of lacoperon. When allolactose is present in the medium lac repressorprotein binds to it            andenables the expression of lac operon genes.            Whenthere is mutation in lac repressor protein to bind to allolactose,the operator is free and allows the expression             oflac operongenes.
      Tryptophan and lactose are twodifferent operons that operate separately.       Hence I don't think therewill be any effect by the induction of lactose in tryptophanoperon.       Hope you are satisfiedwith the answer.

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