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Operons in Prokaryotes

Operons in Prokaryotes. Operons. Group of genes that are transcribed together They are turned ON or OFF as a unit to produce mRNA Promoter RNA polymerase binding site; begins transcription Operator Controls access of RNA polymerase to genes Genes

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Operons in Prokaryotes

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  1. Operons in Prokaryotes

  2. Operons • Group of genes that are transcribed together • They are turned ON or OFF as a unit to produce mRNA • Promoter • RNA polymerase binding site; begins transcription • Operator • Controls access of RNA polymerase to genes • Genes • Genes that need to be transcribed for protein(s)

  3. lac operon • Transcription is started repressor protein is removed from the operator • Lactose breakdown • Lactose  galactose + glucose • WHY would a cell want to do this?

  4. How does lac operon work? • If lactoseis NOT present in cell • operon is “off” • the repressor protein is attached to the operator, which means • No transcriptionof genes • No translation of mRNA • No breakdown of lactose

  5. How does lac operon work? • If lactoseis PRESENT in cell: • Lactose binds to repressor, which changes its shape, making the protein inactive • Remember: Allosteric inhibitor???? • Operon is “on” because the repressor protein is removed from the operator, which means • Transcriptionof genes • Translationof mRNA • Breakdownof lactose

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