Control of Gene Expression

• Why doesn’t every cell express all of its genes?

  The regulation of gene expression conserves energy and space. It would require a significant amount of energy for an organism to express all of its genes, so it is more efficient to turn on the genes only when they are required
• 2 types of mRNA production control

  Negative Transcriptional Control System and Positive Transcriptional Control System
• system in which the regulatory gene product binds to inhibit transcription (the regulatory gene codes for the repressor protein)

  Negative Gene Regulation
• system in which the regulatory gene codes for the expressor protein, one necessary for the gene to be expressed.

  Positive Gene Regulation
• The negative transcriptional control system is characterized by the production of a repressor protein by the regulatory gene.
• The negative system may be either inducible or repressible.
• The lactose operon (lac operon) is an example of a negative inducible system
• The operator locus enables or prevents systemic gene function repression.
• The structural and functional relation between the operator gene and the structural gene was called operon.