Operon Regulation
Promoter Promoter
DNA trpR
Regulatorygene
RNApolymerase
mRNA
3¢
5¢
Protein Inactiverepressor
Tryptophan absent, repressor inactive, operon on
mRNA 5¢
trpE trpD trpC trpB trpA
OperatorStart codonStop codon
trp operon
Genes of operon
E
Polypeptides that make upenzymes for tryptophan synthesis
D C B A
Operon Repressor
DNA
Protein
Tryptophan(corepressor)
Tryptophan present, repressor active, operon off
mRNA
Activerepressor
No RNA made
Repressor
DNA lacl
Regulatorygene
mRNA
5¢
3¢
RNApolymerase
ProteinActiverepressor
NoRNAmade
lacZ
Promoter
Operator
Lactose absent, repressor active, operon off
Operon and Inducers
DNA lacl
mRNA5¢
3¢
lac operon
Lactose present, repressor inactive, operon on
lacZ lacY lacA
RNApolymerase
mRNA 5¢
Protein
Allolactose(inducer)
Inactiverepressor
-Galactosidase Permease Transacetylase
DNA Control stages in Protein Synthesis
Signal
NUCLEUS
DNA
RNA
Chromatin
Gene availablefor transcription
Gene
Exon
Intro
Transcription
Primary transcript
RNA processing
Cap
Tail
mRNA in nucleus
Transport to cytoplasm
CYTOPLASM
mRNA in cytoplasm
Translation
Degradationof mRNA
Polypeptide
CleavageChemical modificationTransport to cellular
destination
Degradation of protein
Active protein
Degraded protein
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