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Gene Regulation: Jssansebastian@dlsud - Edu.ph

The document discusses gene regulation through operons in prokaryotes. It describes operons as genetic regulatory systems where genes coding for related proteins are clustered along DNA and expressed together in response to cellular needs. An operon contains structural genes, a promoter region that binds RNA polymerase, and an operator region that binds repressor proteins to inhibit transcription. Regulator genes produce repressor proteins that bind to the operator to control operon expression. Modulators can bind repressors and change their conformation to activate or deactivate them. The lactose and tryptophan operons are discussed as examples of inducible and repressible operons.

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Kate Camacho
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89 views13 pages

Gene Regulation: Jssansebastian@dlsud - Edu.ph

The document discusses gene regulation through operons in prokaryotes. It describes operons as genetic regulatory systems where genes coding for related proteins are clustered along DNA and expressed together in response to cellular needs. An operon contains structural genes, a promoter region that binds RNA polymerase, and an operator region that binds repressor proteins to inhibit transcription. Regulator genes produce repressor proteins that bind to the operator to control operon expression. Modulators can bind repressors and change their conformation to activate or deactivate them. The lactose and tryptophan operons are discussed as examples of inducible and repressible operons.

Uploaded by

Kate Camacho
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GENE REGULATION

jssansebastian@dlsud.edu.ph
OPERON
 Genetic regulatory system of single-celled
organisms, in which genes coding for
functionally related proteins are clustered
along the DNA, enabling their expression
to be coordinated in response to the
organism’s need.

jssansebastian@dlsud.edu.ph
Components of the Operon

jssansebastian@dlsud.edu.ph
Operon and Prokaryotic Gene Expression

An operon is composed of the following:


 Structural genes- genes that are related and used in a
biochemical pathway.
 Promoter-The nucleotide sequence that can bind with
RNA polymerase to start transcription. This sequence
also contains the operator region.
 Operator-The nucleotide sequence that can bind with
repressor protein to inhibit transcription. 4
Regulator Genes and Repressors
 Regulator gene- This gene produces a protein
called a repressor that can inhibit the
transcription of an operon by attaching to the
operator.

5
Interaction of Modulators and Repressors

 Repressors have allosteric properties. Modulators


can bind to the repressor at an allosteric site
changing the conformation of the repressor, thereby
activating or deactivating the repressor. Usually the
modulator is a product of the biochemical pathway.

6
TYPES OF OPERON
A. Presence of Repressor or Activator
A.1. Negative – Repressor
A.2. Positive – Activator

B. Induce or repress the system


B.1. Inducible – the effector molecule turns
the system on (active)
B.2. Repressible – the effector molecule
turns the system off (inactive)
jssansebastian@dlsud.edu.ph
Lactose Operon

jssansebastian@dlsud.edu.ph
Lactose Operon
RNA polymerase can bind
only with the help of CRP
transcription factor

RNA pol.
AlloLactose

cAMP

CRP Transcription
Factor 1) Allolactose co-
2. cAMP attaches to CRP inducer attaches to
transcription factor when allosteric site of induce
glucose is scarce jssansebastian@dlsud.edu.ph
protein, inactivating it
jssansebastian@dlsud.edu.ph
Seatwork
Which of the following can hydrolyze
lactose constitutively (C) or inducively (I)

1. i p o z
2. i p- o z
3. i- p o z
4. i p o z-

jssansebastian@dlsud.edu.ph
Tryptophan Operon

jssansebastian@dlsud.edu.ph
Seatwork
For the following conditions, indicate
whether the system is on or off?

1. RO P L E D C B A
2. R O P L E D- C B A
3. R- O P L E D C B A
4. R O P- L E D C B A

jssansebastian@dlsud.edu.ph

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