Transcript Lecture on Gene Regulation power point

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
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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
Inducible Operon turned OFF by repressor protein
RNA polymerase: transcription of regulatory gene Animate
first
Repressor protein sits on the operator site
RNA polymerase is blocked access to the structural gene
No transcription of structural gene
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/genetic
s/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.