Question

Describe how the Lac operon works. Be sure to include all the key elements: the components, the process, and the result.

Answer 1

Lac operon is the segment of DNA which is responsible for matabolising the lactose.

It consists of : ( Components)

* Regulatory gene: Regulatory gene encodes repressor. This repressor regulates the expression of lac operon.

* Promoter gene: The promoter gene allows RNA polymerase to bind to the promoter.

* Operator gene: It leads to bind the activated repressor on the operator region.

* Structural gene: It encodes enzyme beta galactosidase, permease and transacetylase from z, y and a gene respectively.

Process:

In absence of lactose or inducer:

The regulatory gene encodes repressor. The repressor remains in active state. Because repressor can not bind to the lactose. The repressor binds to the operator. The RNA polymerase binds to the promoter. But it can not proceed further to structural gene because of hinderance by repressor at operator region.

In presence of lactose:

When lactose is present, then it will bind to the repressor. The repressor becomes inactivated. It can not bind to operator. The RNA polymerase binds to the promoter. It will proceed further to the structural genes. The transcription amd translation occurs. Z gene encodes beta galactosidase. It will break down lactose into glucose and galactose. Y gene encodes permease. It will allow lactose entry in the cell. A gene encodes transacetylase. The detoxification of toxuc compunds occurs by acetylation.

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Results:

The presence of lactose expresses the structural genes. It will allow the break down of lactose.

The absence of lactose does not express the structural gene.

Please look in image: