Gene Regulation

• Warmup: what is meant by gene regulation? Draw an example/model for the control of insulin production? (Hint: look at lac operon in notes from last night!) What is the role of an inducible operon?

Two Types of Gene Regulation • Inducible Operon: basically is turned off until turned on (inducer warps

shape of repressor protein and it falls off the operator)• Ex. Lac Operon

• Repressible Operon: turned on until turned off (repressor protein does not have the correct shape to fit on the operator until a corepressor compbines with repressor and it now fits on the operator site)

• Ex. Tryptophan operon

Gene Regulation

Gene structure: regulatory gene: promoter: structural gene: terminator

RNA polymerase: transcription of regulatory gene first

Repressor protein sits on the operator site

RNA polymerase is blocked access to the structural gene

No transcription of structural gene

                                                Animate

Inducible Operon turned OFF by repressor protein

Inducible operon is turned ON by presence of Inducer

When lactose is present it binds to the repressor protein altering the proteins shape.

The repressor protein falls off the operator site.

RNA polymerase can now transcribe the structural genes.

Feedback Loop: http://www.phschool.com/science/biology_place/biocoach/lacoperon/feedback.html

“Lactase” (b-galactosidase) cuts up lactose into glucose and galacatose

When there is no lactose, the repressor protein is free to bind to the operator.

RNA polymerase is now blocked from transribing the structural gene

Repressible protein:

http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/genetics/protsyn/regulation/ronorep.html

Repressible protein cannot bind to the operator.

RNA polymerase transcribes gene

If co-repressor is present it can then bind to the repressor giving the correct shape and sits on the operator.

RNA polymerase is now blocked and the operon id turned OFF.