Chapter 14 Flashcards
Conserves energy
Proteine produce as needed
Constitutive gene
Unregulated & have essentially constant levels of expression
Bacterial gene regulation
Occurs at Transcription leve/or Control mRNA translation rate, or regalate proteine.
Eukaryotic gene regulation
Transcriptional regulation, RNA processing, translation, post- translation
Repressors
Inhibit Transcription
negative control
Activators
Increase the rate of Transcription
positive Control
Small effector molecole
Binds to regulate Transcription factor & cause conformational change
2 domains in regulatory Transcription factors.
Site where protein binds to DNA
Site for small effetto molecole
Operon
in batteria.
A cluster of genes under transcriptional Control of One promoter.
Polycistronic mRNA
Encodes more than 1 protein.
Lac operano
in e.coli
Contains lactose metabolism genes
LacP
Promoter
3 structural genes
Lac Z -β-galactosidase (enzyme)
Lac y- lactose permease (transporter)
Lac A- galactosidase transacetylase (modifies lactose)
LacO- operator-
Provides building site for Repressor protein
CAP site
Activator protein binding site
LacL gene-
Codes for lac Repressore
In absent of lactose
Lac repressor protein binds to nucleotide, prevents RNA polymers from transcribing LacZ,LacY,LacA
When lactose is present
4 allolactose molecules binds to Lac repressor prevents repressor from binding
CAP ( catabolite activator protein)
An activator protein
When lactose & glucose are high
Lac operon is shut off
When lactose is high & glucose is low
Lac operon is turned on
When lactose is low & glucose is high / low
Lac operon is off
Low tryptophan level
Trp repressor can’t bind & operon genes transcribed
High tryptophan levels.
Tryptophan turns off the trp operon
How does tryptophan acts?
Like a small repressor molecule/ corepressor.
Inducible
Allolactose induces transcription
When does lac repressor binds to it’s operon??
In absence of it’s small effector molecule
When does trp binds to it’S operon?
In presence of it’s small effector molecule
Repressible
Tryptophan represses transcription
Activators binds to….
Enhancers
Repressors binds to….
Silencers
Binding to GTFs
This can enhance or prevent theformation of the pre- initiation complex
Mediator
Activators stimulate the function of mediator by allowing faster initiation
Histone acetyltrasferase
Attaches acetyl groups to histone amino tails so they don’t bind DNA as tightly
