Chapter 7.4 Flashcards
1
Q
What is an operon?
A
- common in prokaryotes
- share a single promoter region on the DNA sequence
- > these genes are transcribed as a group
2
Q
Describe the two types of operons
A
-inducible systems and repressible systems
3
Q
Describe an inducible system
A
- there is a repressor
- > the repressor is tightly bound to the operator system
- > will not let the RNA polymerase get from the promoter to the structural gene because the repressor is in the way
- to remove the repressor from the operator
- > an inducer must bind to the repressor protein
- > this allows for the RNA polymerase to move down the gene
4
Q
What is the relation between an inducible system and competitive inhibition
A
- like competitive inhibition
- > as the concentration of the inducer increases
- > it will pull more copies off of the operator region
- > freeing up those regions for transcription
5
Q
What type of system is a lac operon?
A
- it is an inducible system
- > lactose can be digested by bacteria but it is more energetically expensive than digesting glucose
- > therefore, bacteria use this option when lactose is high and glucose levels are low
-lac operon is induced by lactose
6
Q
Describe a repressible system
A
- allows for constant production of a protein product
- the repressor made by the regulator gene is inactive until it binds to a corepressor
- > this complex then binds to the operator site to prevent further transcription
- > often the final structure serves as a corepressor(negative feedback)
7
Q
What is an example of a repressible system
A
- trp operon
- > when tryptophan is high in the local environment, it acts as a corepressor
- > it then binds to a repressor protein and then this complex binds to the operator site to prevent the translation of the tryptophan protein
