Operon System

• Operon system makes sure that there is no energy being wasted. Operon systems only exist in prokaryotes, since eukaryotes use TATA box for the control. There are two types of operon system: 1) repressible and 2) inducible. [Repressible---on to off/ Inducible---off to on] For the pGLO lab we did in class, it was an inducible operon system. Arabinose was brought into the system from an outside source, and it was added in front of the pGLO gene. Then, it produced protein to help it grow. Yet, overtime, the bacteria would not glow anymore due to the fact that the system would create arabinase that digests away the arabinose.  
  
  
  
  
  
  

  

  WOW! We created bacteria that glows in the dark

  
  
• Operon system is a genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This system allows protein synthesis to be controlled coordinately in response to the needs of the cell. (By providing the means to produce proteins only when and where they are required). 
• A typical operon consists of a group of structural genes that code for enzymes involved in a metabolic pathway, such as the biosynthesis of an amino acid. These genes are located contiguously on a stretch of DNA and are under the control of one promoter (a short segment of DNA to which the RNA polymerase binds to initiate transcription). A single unit of messenger RNA (mRNA) is transcribed from the operon and is subsequently translated into separate proteins.
• The promoter is controlled by various regulatory elements that respond to environmental cues. The regulator protein can either block transcription, in which case it is referred to as a repressor protein; or as an activator protein it can stimulate transcription. Further regulation occurs in some operons: a molecule called an inducer can bind to the repressor, inactivating it; or a repressor may not be able to bind to the operator unless it is bound to another molecule, the corepressor. Some operons are under attenuator control, in which transcription is initiated but is halted before the mRNA is transcribed.