Control of gene expression in Prokaryotes

Enzymes
1. Inducible
2. Constitutive
3. Repressible
Regulation control
1. Positive
2. Negative
Regulatory elements
1. Cis-acting
2. Trans-acting
Lac operon
1. Structural genes
  1. lacZ
  2. lacY
  3. lacA
2. Negative control
  1. Transcription only occurs when the repressor fails to bind to the operator region
3. Model
  1. Proved by analysis of lac expression in the absence or presence of lactose in partial diploid merozygotes
Catabolite activating protein
1. Involved in catabolite repression
  1. repress expression of the lac operon when glucose is present
2. In the absence of glucose and presence of lactose, CAP exerts positive control
  1. binding the CAP-binding site and facilitating RNA polymerase binding at the promoter
3. Cyclic adenosine monophosphate is required for CAP binding
  1. Glucose represses expression of adenylyl cyclase
    1. the enzyme that catalyses the production of the trp structural genes
Trp operon
1. Transcription can occur even when the operon is repressed in the presence of tryptophan

Resource summary

	Created by Abbey Roberts over 10 years ago