L12 Drosophila, setting up the body axes Flashcards
What is established along the anterior-posterior (A/P axis)?
A head, a tail, a thorax, and abdominal region are formed.
The thorax and abdomen are SEGMENTED (composed of repeating units)
List the four regions defined by the Dorsal - Ventral (D/V) axis in Drosophila
-Ventral most mesoderm
-Ventral ectoderm
-Dorsal ectoderm
-Amnioserosa (an extraembryonic tissue
What is the point of Antero-Posterior patterning?
It’s how the embryo determines which end will become the head (anterior) and which will become the tail (posterior)
What is required for the mother to provide the INITIAL information to set up the two main perpendicular axes?
This requires the action of MATERNAL GENES (genes that need to be present in the genome of the MOTHER)
What are the three classes of maternal genes that set up the A/P axis?
- Bicoid
- Nanos
- Torso Signal.
What is a Morphogen?
A morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its concentration.
In simpler terms, it’s a substance that helps determine the fate of cells based on how much of it they are exposed to
What does bicoid do in A/P axis of synctial embryo?
Its RNA is localized at the anterior of the egg hence why there’s a higher concentration on the anterior side compared to the posterior side
What is Nanos required for?
This protein is required for proper formation of the posterior segments.
In summary what do maternal genes do to the A/P axis in fruitflies?
1) Maternal genes, like bicoid and nanos, lead to the formation of protein concentration gradients within the egg (bicoid most concentrated at anterior end of egg,nanos being at the posterior (tail) end of the egg)
2) Protein gradients acts as morphogens, providing positional information
Where is the Torso signal present?
- Torso receptor is present everywhere.
- “Torso-like” protein is only present at the polar regions of the egg
What is the role of Torso signal?
The “torso signal” refers to a crucial signaling pathway in the early development of Drosophila melanogaster (fruit flies) that plays a key role in establishing the anterior-posterior (AP) axis
What is the D/V polarity?
Dorsal-ventral (D/V) polarity refers to the establishment of the back-to-belly axis in developing embryos.
How is the D/V axis set up?
The D/V axis is set up due to the asymmetric position of the nucleus
What is Spätzle-Toll?
Spätzle = ligand protein
Toll = receptor
When binded together, it leads to a high concentrations of the Dorsal protein on ventral side, determining cell fate
Which cell - cell signalling is required to set up both anterio-posterior and dorso-ventral axes?
Gurken
Explain why the Toll receptor is only activated in the Ventral side
Localised enzyme “Pipe” creates active Spätzle ligand on ventral side
