Gene Control Mechanisms Flashcards
In a multi cellular organism, what is significant about theircells?
Their cells all have the same genetic information.
Each cell makes a different set of proteins.
What happens to the proteins in each cell over time?
They change.
What is the state of most genes in most cells most of the time?
Turned off.
What is another word for a transcriptional control part?
Operon
What is an operon?
a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter.
What is a promoter?
A sequence of DNA rich in A + T that is found upstream of TAC start code.
What bonds to a promoter?
RNA polymerase
What is an operator?
A sequence of DNA beside promoter. To which a repressor protein binds.
What bonds to the operator?
A repressor protein.
What happens if a repressor protein bonds to an operator?
Transcription will not occur because RNA polymerase will not be able to bond to the promoter.
What does a repressor protein do?
Binds to operator. UNLESS it binds to inducer first.
What happens when a repressor protein binds to an inducer?
The shape of the repressor is changed and transcription occurs.
What is an inducer?
A molecule that binds to repressor and prevents the stopping of transcription.
Why is the gene to make trp usually on?
Because cells need it, and it is rare in the environment.
Why does trp act as a co-repressor if present?
Because it is metabolically expensive to make, so if it is available somewhere else, you shouldn’t make it.
