I need a note on regulation of gene expression in prokaryotes.

I need a note on regulation of gene expression in prokaryotes.


1 Answers

Simran Vinaik
askIITians Faculty 1230 Points
6 years ago
E. coli can use either glucose or lactose as the sole source of carbon and energy. When E. coli cells are grown in a glucose-containing medium, the activity of the enzymes needed to metabolize lactose is very low.?

When lactose is absent the Repressor is transcribed and translated from I (regulatory) gene. This repressor goes and binds to operator region and prevents Rna polymerase from transcribing the metabolizing enzymes. At this time gene expression of Lac Operon is shut off.

When these cells are switched to a medium containing lactose but no glucose, the activities of the lactose-metabolizing enzymes increase. The lactose inactivates the repressor and RNA polymerase transcribes 3 genes – lac Z,Y,A in lac operon.
  • The lacY gene encodes lactose permease, pumps lactose inside the cell.
  • The lacZ gene encodes β-galactosidase,which splits the disaccharide lactose into the monosaccharides glucose and galactose.
  • The lacA gene encodes transacetylase.
This is how gene expression is regulated in absence and presence of lactose.
554-2273_lac operon.jpg

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