Triggering Differentiation Flashcards
How is differentiation triggered?
- Stem cells receive differentiation signals that tell them what type of differentiated cell to produce
How are differentiation signals received?
Differentiation signals are received via cell surface receptors that transmit the signal into the cell, leading to changed is gene expression
Stem cells have multiple different receptors. When one or more receptor is activated it starts the process of differentiation.
What factors decides what progenitor a stem cell turns into?
Differentiation into a specific progenitor depends on
1) What the body needs (e.g RBCs after bleeding)
2) Signals that tell the cell to differentiate
3) Combination of signals with which then the stem cell will turn into a different cell.
How does differentiation affect gene expression?
Differentiation changes which genes are switched on and off.
It turns specific genes on.
How are genes switched on and off?
By changing the structure of DNA in the nuclease
chromatin - DNA bound to a protein
Histone protein - Helps package DNA.
What are the different degrees of DNA packaging?
1) Heterochromatin - tightly wrapped up DNA that can’t be read or transcribed (i.e silenced).
2) Euchromatin - lightly packaged DNA which is accessible for transcription
What type of packaging is most common in stem cells and differentiated cells?
In stem cells, most of the DNA is found as euchromatin
As the cell becomes differentiated, more genes are silenced and more DNA is found as heterochromatin as the cell becomes specialised for its function.
How is movement between Heterochromatin and euchromatin controlled?
Through epigenetics.
Through the use of enzymes which attach or detach methyl or acetyl groups to the DNA or histones.
What does methylation do?
Methylation adds a methyl group to the DNA/histone making it more tightly packaged and thus silencing the gene.
What does Acetylation do?
Acetylation adds an acetly group to the DNA/histone, unpackaging the histone and making it more accessible.
What does demethylation do?
Demethylation removes a methyl group from the histone making the DNA more accessible.
What does deacetylation do?
Deacetylation removes an acetyl group from the DNA/histone making DNA less accessible - thus silencing the gene.
