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Gene Expression Regulation: trp Operon

Gene Expression Regulation: trp Operon. trp Operon. trp – tr y p tophan The genes of the trp operon are used to make the amino acid tryptophan. It is turned off when enough tryptophan is in the cell. Tryptophan is the effector molecule. trp Operon.

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Gene Expression Regulation: trp Operon

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  1. Gene Expression Regulation:trpOperon

  2. trp Operon • trp – tryptophan The genes of the trp operon are used to make the amino acid tryptophan. It is turned off when enough tryptophan is in the cell. Tryptophan is the effector molecule.

  3. trp Operon Operon codes for 5 genes – found in E. coli Five polypeptides combine to make three enzymes. • each enzyme participates in a step to make tryptophan

  4. Repressor Protein repressor protein (trpR) • binds to operator when tryptophan is present • prevents RNA polymerase from transcribing genes when bound to operator • transcribed as a different gene from trp operon When do you want the repressor to bind / not bind to the trp operon?

  5. When tryptophan needs to be made: • enzymes are required to make tryptophan • repressor is NOT bound to operator • transcription can proceed

  6. When cell has enough tryptophan: • tryptophan binds to repressor • repressor can now bind operator to prevent transcription

  7. Effector Molecule Since tryptophan is the molecule that determines when the operon is turned on or off, it is known as an effector molecule. corepressor – effector molecule that binds repressor protein to cause it to bind to the operator

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