11. The lacZ gene, responsible for lactose metabolism is an inducible gene regulated by a repressor...

11. The lacZ gene, responsible for lactose metabolism is an inducible gene regulated by a repressor protein. Answer the following questions regarding how this gene is regulated (3 pts each) a. What is the default setting in reference to the expression of lacZ? b. What role does lacI play in regulating the system? c. What happens when the system is exposed to lactose? d. What happens after the cell digests the lactose supply

Expert Solution

Ans. Lac Z is a gene of beta galactosidase, regulated by an upstream repressor gene which encodes repressor protein.

a. There are many components in lac operon system as-

Lac I gene for repressor protein

LacP promoer of lac I (RNA polymerase binding )

Lac O operator of lac Z (repressor binding takes place)

Lac Z gene for beta galactosidase,

Lac Y gene for permease,

LacA gene for Transacytylase.

When lactose is absent in the cell and repressor binds on the operator in this conditions RNA polymerase unable to bind on promoter of beta galactosidase gene because repressor has overlapping binding site with promoter (where RNA polymerase is binds)

b.

In normal conditions When lactose is absent in the cell repressor protein binds to the operator of lac z gene and inhibits synthesis of lac Z gene.

But hen lactose is present in the cell repressor protein get engaged with the lactose and RNA polymerase able to bind on lac Z promoter and able to synthesis gene for beta galactosidase.

c.

When system exposed to the lactose that means cell required an enzymes that catalyse their metabolism. Hence in the presence of lactose beta galactosidase will synthesize.

d.

When all lactose present in the cell are digested then repressor protein bound to the lactose become free and again binds to the operator of the gene and inhibits RNA polymerase binding and this beta galactosidase synthesis.

gladiator answered 1 year ago

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