Gene regulation in eukaryotes Flashcards
if cells arent efficient with their energy, what will happen to them?
they will be outcompeteted and will die out
why the need for gene regulation?
as with prokaryotes there is a need to be able to respond to cues from the environment – so that efficient use of energy resources, response to stressors and protection from attack can be regulated effectively.
many eukaryotes are…
…complex multicellular organisms with highly differentiated cells
What must cells go through in order to become differentiated?
complex developmental changes
in order to become differentiated cells must go through complex developmental changes.
What do these changes necessitate?
different genes being turned on at the correct times to produce a mature cell which will have a different complement of proteins from its precursor and also from other types of differentiated cell
What can a Haematopoietic stem cell differentiate into?
can differentiate into any kind of BLOOD cell. Can become a Common myeloid progenitor cells or common lymphoid progenitor cells.
What do Haematopoietic stem cells require?
signals from the body, using receptors. These signals tell them what kind of signals the body needs.
What needs to happen to hematopoietic stem cells in order to become different cells?
In order to become these different cells, different genes need to be turned on or turned off, and in the correct order. Without this, there are no differentiated cell types, no cell differentiation.
eukaryotic genes are more complex than…
…those of prokaryotes.
what is the open reading frame (ORF) composed of?
exons within the gene
what is the open reading frame (ORF) split by?
intervening non-coding DNA in the form of introns (not always)
what are introns?
intervening non-coding DNA
in order to be expressed as a transcript from a eukaryotic, the gene has to be ….
… processed to remove the introns
what do most eukaryotic cells have?
Most eukaryotic genes have exons and introns.
what are the three types of RNA Polymerase?
RNA Polymerase I
RNA Polymerase II
RNA Polymerase III
What does RNA Polymerase I do?
rRNA genes – the functional components of ribosomes
What does RNA polymerase II do?
protein coding genes, miRNA, snRNA
What does RNA polymerase III do?
tRNA, some rRNA, some snRNA
How many types of RNA polymerase in eukaryotes?
3 types of rna polym in eukaryotes.
What does transcription depends upon?
The formation of a preinitiation complex (PIC) comprising of basal transcription factors (TF).
What do basal transcription factors consist of??
TFIIA, TFIIB, TFIIF, TFIIE, TFIIH, and TFIID.
What is TFIID?
TFIID is a complex of different protein subunits including TATA Binding Protein.
Where there is a TATA Box in the promoter this protein binds to….
…DNA at that point helping to recruit RNA polymerase II to the transcription start of a gene.
the complexity of promoter elements varies…
…hugely in eukaryotes
simple single-celled eukaryotes commonly have promoters that are…
…simple and proximal to the gene itself
simple single-celled eukaryotes commonly have promoters that are simple and proximal to the gene itself whilst multicellular organisms may …
…have regulatory elements many kilobases away from the gene itself.
What does the core promoter enable?
enables the transcription initiation complex to bind to the promoter.
What does the core promoter have upstream?
have responsive elements upstream of the core promoter (up to several kilobases).
What is the purpose of the responsive elements upstream of the core promoter?
proteins bind to these and either enhance of silence the genes by interacting with proteins in the transcription initiation complex.
Cell-specific modules are specific to…
…certain cell types (cell specific).
Purpose of Cell-specific modules ?
ensuring that gene expression only takes place in the correct cell.
regulation can occur at…
…multiple points.
Where does gene regulation occur?
1 - DNA unpacking/alteration (methylation, acetylation etc)
2 - regulation at the level of transcription
3 - regulation at the processing stage
4 - regulation of splicing to form different proteins
5 - post-transcriptional regulation – mRNA stability
6 - regulation of translation
7 - post-translational regulation (e.g. phosphorylation)
8 – protein stability
when does elongation occur?
elongation occurs after transcription is initiated and the gene is transcribed by complementary base-paring of ribonucleotides to the template (non-coding) strand
When does termination occur?
termination occurs after the polyadenylation signal is transcribed
What happens after termination?
RNA polymerase dissociates from the DNA strand and the pre-mRNA
unlike in bacterial genes regulation in eukaryotic genes may take place over …
… a large distance.
DNA is…
…looped
DNA is looped and activators and repressors connect their binding regions (enhancers and silencers) with …
…the transcription initiation complex via mediator proteins
What are the binding regions of activators and repressors?
enhancers and silencers
What must happen to eukaryotic transcripts before export to cytoplasm and translation?
unlike in prokaryotes – eukaryotic transcripts have to be processed before export to the cytoplasm and translation
