Flashcards in embryology and inductive signals - lecture 9 Deck (21)
What do transcription factors do?
Bind to the DNA , stimulating gene expression. Determine cell fates by being activated at different points in development
What are inductive signals?
messengers/signals which activate different transcription factors
How do the concentrations of the inductive signals change?
Further from the signalling cells produce inductive signals , induce lower concentration of the signal
What is the actual mechanism of inductive signals
Receptors span the plasma membrane.
Protein enters nucleus and activates the transcription , to activate transcription of the genes.
What is a homeotic gene?
ny of a group of genes that control the pattern of body formation during early embryonic development of organisms
What happens when you separate an fertilised embryo , but both contain a grey crescent?
What happens when the grey crescent isn't present?
Only a belly piece develop
What happened when a dorsal lip is cut out and transferred to the ventral half of another embryo?
Resulted in a two headed embryo. Therefore the dorsal lip is responsible for the spinal region
Who was given the noble prize for discovery of the function of the spemann
What change in fate does the Spemann organiser graft make?
It induces a Dorsal fate in cells that would otherwise follow a ventral fate. Forms a backbone instead of belly
How can you find the gene responsible for different embryological growth?
Make a plasmid library. Inject mRNA into the embryo, lots of protein is then made by the mRNA.Does this alter protein development
Why is UV used to inhibit dorsal structures?
Then lots of different mRNAS were injected to find one which rescued head development
What is Noggin?
Secreted signalling molecule that can promote dorsal structures
What is the correct amount of Noggin for normal development
How to find where the gene is expressed?
- Fix the embryos
- RNA probe added which binds to floating mRNA
- Antibody (labelled with an enzyme) binds to a RNA complex
- Embryos washed , antibody has an enzyme attached which allows for production of a coloured ppt
This is called in situ hybridisation
Where is noggin expressed?
In the Spemann organiser
What fates do cells far form the Spemann organiser follow?
ventral fate . Cells close follow dorsal fates
What happened in Hans Spemann and Hilde Mangold experiments?
- removed the Spemann organiser (dorsal lip) which forms on the side of the embryo which will give rise to the dorsal side - the side with the brain and spinal chord
- grafted to the ventral side
- made an embryo with an extra head and spinal chord
How was Noggin identified as an inductive signal/ inducing factor?
- plasmid library was made which has many random genes
- Each plasmid was used to make mRNA
- Each mRNA was injected into separate Xenopus laevis embryos , in order to make the proteins that the RNA codes for
- some embryos treated with UV to lose their dorsal structures
- RNA injected into these embryos that promotes dorsal structure again , ended up being noggin
What role does signal transduction play?
relays the 'message; from the extracellular signal from the membrane to the nucleus where it activates gene expression via a transcription factor