The lac operon

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  • Created by: Steff06
  • Created on: 02-05-16 14:59
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  • The lac operon
    • B-galactosidase catalyses the hydrolysis of lactose to glucose and galactose. Lactose permease transports lactose into the cell.
    • Operon = A length of DNA, made from structural genes and control sites.
      • Operon consists of the structural genes, the operator region and the promoter region.
    • Structural genes = Z codes for B-galactosidase, Y codes for lactose permease. Each consists of a sequence of base pairs that can be transcribed into mRNA.
    • Operator region = (O) A length of DNA next to the structural genes. It can switch them on and off.
    • Promoter region = (P) A length of DNA to which the enzyme RNA polymerase binds to begin transcription of structural genes Z and Y.
    • The regulator gene (I) is not part of the operon. It codes for a repressor protein and blocks the promoter region.
    • RNA polymerase binds with the promoter region.
    • The regulatory gene transcribes and translates to synthesise a repressor protein.
    • If the repressor protein is removed, transcription will occur.
    • Repressor protein binds to the operator region and blocks some of the promoter region, preventing RNA polymerase from binding.


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