Gene Regulation in Bacteria 2 Flashcards
What are repressible operons?
Operons that are switched off when there is sufficient amounts of the product.
Give an example of a repressible operon.
The trp operon.
Outline how the trp operon functions.
When the trp levels are low, there is a high level of transcription of the trp operon, but it is switched off when there is sufficient product in the cell, so no wasted energy or resources.
When the level of trp increases, the transcription of the trp operon decreases, and is switched off as it is not needed.
Describe the structure of the trp operon.
Operon consists of (in order):
>trpR gene- repressive regulator, upstream to the promoter… has its own promoter.
> Promoter and operator.
> Leader sequence… important in regulating the trp operon… special sequence in the leader sequence… attenuator sequence trp a.
> Five different structural gene trpE/D/C/B/A, involved in enzyme production, and will give rise to tryptophan… multi-polypeptide molecule… cleaved into different proteins.
Explain how the trp operon is under negative control.
When tryptophan is present… operon is repressed… Under negative control of the active repressor… which is the co-repressor tryptophan bound to the aporepressor.
How does the repressor protein repress transcription of the trp operon?
trpP has a separate promoter for RNA polymerase, where it binds and synthesises mRNA for a regulatory protein.
