BACTERIAL OPERONS
Parts:
- The Promoter
o The region where RNA polymerase is going to bind
o Marks the start of the gene, but does not contain DNA
that is expressed
- The Operator
o DNA sequence after the promoter that controls
whether or not RNA polymerase will proceed
o Does not contain DNA that is expressed
- The Genes
o The actual genes involved in the desired function
o All in a straight line, one after another
o The DNA that is expressed
- The Regulatory Gene
o not an actual part of the operon
o constantly expressed (on), but in low amounts
o produces a protein called the repressor, can be active
or inactive depending on the operon
- Two Types of Operons
- Inducible Operon
o Operons with and active repressor need to be turned
on, when active it will bind to the operator
o It will not allow RNA polymerase to pass, blocking
transcription
o Ex. Lactose operon, needs to be broken down because
we can’t digest disaccharides, only monosaccharides
o Inducer is a molecule that will bind to the repressor and
deactivate it (what lactose is)
- Repressible Operon
o The regulatory gene makes the repressor in an inactive
state instead
o Making transcription allowed to always occur because
nothing is blocking it
o Ex. Trp operon (or arg operon)
o Amino acids are vital for making protein so we always
want it to be turned on, always want to make
tryptophan.
o DEFAULT ON!
o A Corepressor is a molecule that will bind to the
inactive repressor and activate it