Gene Regulation
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Gene regulation
The process of controlling which genes are expressed and the rate at which they are expressed Controls the amount of proteins present in a cell Can occur at any stage of protein synthesis
X inactivation
One X chromosome in each cell is randomly inactivated Happens during embryonic development
Barr body
The X chromosome that is inactivated and condensed
Lac operon
A unit of DNA Contains • 3 structural genes • operator • promotor region Responsible for breaking down lactose
Lac operon structural genes
Lac Z Lac Y Lac A Code for enzymes that break down lactose
Two main types of genes in prokaryotes
Regulatory genes - code for transcription factors Structural genes - code for other types of proteins
What is lac I?
Regulatory gene that codes for lac repressor (a transcription factor) Next to lac operon
RNA polymerase binds to : Lactose binds to : Lac repressor binds to :
RNA polymerase binds to promotor Lactose binds to lac repressor Lac repressor binds to operator
When there is little lactose
Lactose will not buying to lac repressor
When no lactose binds to lac repressor,
Lac repressor will bind to operator
When lac repressor binds to operator
RNA polymerase will not bind to promotor region
When RNA polymerase does not bind to promotor region
Genes will not be transcribed Lac Z, Y, A
When genes not transcribed
Enzymes that break down lactose will not be produced
When enzymes that break down lactose are not produced
Lactose will not be broken down, so there will eventually be more lactose