Question

10. Using the lactose operon as an example, diagram and explain gene expression through the action of a promoter, an operator, structural genes, and a repressor protein when lactose is present and when lactose is absent. 11. Define and give examples of epigenetic control of gene expression.

Answer 1

Answer-

According to the given question-

Regulator kene RNA pol- 1 DNA I laci operator 116 structorals gene HH lac 2 lac y lac A AL T 1 1 Q-galeetosidase Transactylase R-q aloetosidase Bagalactosidlaje permeape promoter Repressor gene 1 Repressor protem

We know that the lac operon is found in E.Coli consist of -

Promoter region - For RNA Polymerase binding and after binding RNA Polymerase transcribes the gene.

Operator region -

Three structural gene -

Lac Z code for Beta-galactosidase,

Lac Y code for Beta-galactosidase permease

Lac A gene Beta-galactosidase Transacetylase.

There is a Lac I or repressor gene, code for repressor protein.

Condition 1- when  Lactose present - then the lactose binds with the repressor protein and causes the change in its shape , due to which repressor molecule unable to attach and bind with the operator region and RNA Polymerase binds with promoter region and move along the operator region and Transcribes the gene required for lactose metabolism .

Condition 2 When lactose absent, - Then the repressor protein binds with the operator region, the RNA polymerases binds with the promoter region but unable to cross the operator region occupied by repressor protein, due to which the transcription of gene required for lactose metabolism does not occur.