Please enable JavaScript.
Coggle requires JavaScript to display documents.
Regulation of Transcription (The lac operon (laci gene upstream of lac…
Regulation of Transcription
The E.coli model
Promoter sequence in DNA tells RNAP where to start
6 bases -35 and -10 from transcription start are binding sites for RNAP
No RNAP is a perfect match for the -35/-10 sequences as the rate of transcription would be too high
Transcription factors
Negative control
Degrade repressor when you want to turn gene on
Inducible transcription = Inducer binds to repressor so it cant bind to promoter
Repressor binds to promoter and blocks RNAP
Repressible transcription = Co repressor needs to bind to DNA for repressor to work
Promoter active if no transcription factor
Positive control
Promoter inactive if no transcription factor
Activator binds to promoter and helps RNAP bind
Degrade activator when you want to gene off
The lac operon
Turned on and off depending on the concentration of lactose in the environment
Polycistronic for genes that have a function in lactose metabolism
laci gene upstream of lac operon codes for repressor that turns lac operon off by binding to lac operon operator when there is no lactose
if the lac operon operator is mutant the repressor cant function
lactose binds to laci so it cant bind to lac operon operator
Glucose strarvation
Synthesis of cyclic adenosine monophosphate (cAMP)
cAMP bind to CRP
cAMP-CRP complex is a =n activator
Eukaryote
More transcription factors because different cells express genes differently
Gene or cell specific
Activators and repressors
coactivators and corepressors
Generic
RNAP
Basal transcription factors (help RNAP bind)
Promoters
Core promoters overlap transcription start and bind general transcription factors (GTF)
Chromatin is a repressor so ground state of transcription is off
Activator that remodels chromatin needed at all promoters
Enhancer/ proximal promoters bind activators
Silent genes
On condensed chromatin
Methylation of repressor
Gal 1 gene
Yeast
Negative control
In the absence of galactose gal80 represses gal 4 (gal 4 needed as it acetylates)
Interferon beta genes
Activators bind to enhancer
Co activators modify chromatin
X inactivation
One x chromosome in female gamete inactivated
= bar body seen in female cells