Transcriptional level - Prokaryotes

    Cards (12)

    • Lac operon controls the production of lactase and two other structural proteins.
    • Lac operon is an inducible enzyme, only synthesised when lactose is present.
    • The inducible nature of Lac operon helps bacteria from wasting energy and resources.
    • Lac operon consists of a promoter for a structural gene, an operator, a structural gene lacZ which codes for lactase, a structural gene lacY that codes for permease, and a structural gene lacA which codes for transacetylase.
    • To the left of Lac operon, there is a promoter for a regulatory gene and a regulatory gene lacl that codes for the lac repressor protein.
    • When lactose is absent, the regulatory gene is transcribed and translated to produce lac repressor protein.
    • Lac repressor protein binds to the operator region of lacZ when lactose is absent.
    • RNA polymerase is unable to bind to the promoter region when lactose is absent.
    • No lactase enzyme is synthesised when lactose is absent.
    • When lactose is present, the uptake of lactose by a bacterium distorts the shape of the lactose binding site in the repressor protein, causing it to no longer bind to the operator site.
    • RNA polymerase is able to bind to the promoter region and transcription takes place when lactose is present.
    • Enzyme lactase is produced when lactose is present.
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