Gene expression Flashcards
Why must gene expression be tightly controlled?
To ensure vital proteins are produced when required and that energy is not wasted on the production of proteins with no use for the cell.
What are transcription factors?
Transcription factors are proteins that bind to promoter sequences and enhancers, which regulate gene expression by increasing or decreasing the likelihood of transcription.
What transcribes more efficiently, a strong promoter with strong affinity for RNA polymerase or a weak promoter?
A strong promoter will transcribe more efficiently as RNA polymerase has difficulty attaching to a weak promoter.
How is the lac operon switched on?
The lac operon is switched on when lactose is present, binding to a repressor protein which becomes altered. The repressor protein is no longer able to bind to the operator, meaning RNA polymerase can bind to the promoter, switching the lac operon on.
How is the lac operon switched off?
The lac operon is switched off when the repressor protein, which is produced continuously, binds to the operator in the absence of lactose. This means RNA polymerase cannot bind to the promoter and therefore cannot transcribe the structural genes, leading to them being turned off.
Why is the lac operon a good way of controlling gene expression?
Saves energy and resources, increases efficiency of transcription and all related genes are under one point of control.
