Lecture 6 - Control Of Gene Expression: Transcriptional Control Flashcards
What does it mean by translation and transcription being coupled in bacteria?
They happen in the same place, and as soon as mRNA is transcribed RNA polymerase binds
What differences does bacterial gene expression have from eukaryotic?
No nuclear membrane, one cytoplasmic compartment, no histones, coupled transcription and translation
What is the subunit in bacteria called that helps RNA polymerase bind to the promoter?
Sigma factor
What determines which DNA strand is transcribed?
The polarity of the promoter that orients the polymerase
What determines which DNA strand is transcribed?
The polarity of the promoter that orients the polymerase
What regions of bacterial DNA are transcribed?
Terminator NOT promoter
What is an operon?
Clustered genes of related function eg E.Coli Lac operon
What occurs to operons during transcription and translation?
All genes in the operon are transcribed together and translated to give separate proteins per operon
What does the Lac operon do in its default state?
When lactose is absent, the Lac l gene produces a repressor that switches the Lac operon off (negative gene regulation)
What occurs to the Lac operon is LACTOSE is present?
Lactose binds to the repressor inactivating it, therefore RNA polymerase binds to the Lac operon and lactose is metabolised and transported
What is positive gene regulation of the Lac operon?
When glucose AND lactose are present, E.coli uses glucose however when glucose is low, a catabolise activator protein (CAP) is activated by cAMP and attaches to the promoter of the Lac operon to increase affinity of RNA polymerase to increase transcription
What do eukaryotic promoters contain promote the binding of general can transcription factors?
sequences such as TATA that occurs -30 bases before the transcription start site helping TBP bind
What are enhancers?
Activator proteins that are bound to regulatory DNA sequences that allow for receptors to bind meaning substances such as cortisol can then bind and initiate transcription
What is Epigenetics?
The study of changes in organisms caused by the modification of gene expression rather than the alteration of the genetic code
What occurs when DNA is methylated?
Gene expression is repressed due to methyl groups binding to C or G bases that if in enhancers or promoters, blocks transcriptional factors
What do DNA methyltransferases do to hemimethylated DNA?
Add another methyl mark in activating the DNA since the histones and DNA are tightly wound
When does a wave of demethylation occur?
After fertilisation
In what 4 ways can histones be covalently modified on their N terminal tails?
Acetylation, phosphorylation, methylation, ubiquitylation
