CB40: Axis formation & organogenesis Flashcards
Define organising centres.
Groups of cells that secrete signals for other embryo cells.
State 2 main organising centres of vertebrates.
Node & notochord
What proteins are secreted by the node?
Nodal
Noggin
FGF
How does the node act as an organising centre?
It tells the embryo to gastrulate. During gastrulation, it tells cells which germ layer to migrate to and whether they are anterior or posterior cells.
Define morphogens.
Dosage-dependent proteins that give a signal.
What is Shh used for?
To tell neurons whether to become motor neurons and to pattern digits.
Define homeotic mutation.
The transformation of 1 body segment into another related one.
What are homeotic genes?
They are transcription factors with a DNA binding domain.
Where are homeotic genes found?
They are found in different body segments.
Explain colinearity wrt Hox genes.
It means that the order in which Hox genes appear on the chromosome is the order in which they appear on the body.
In humans, where are Hox genes expressed?
In the vertebral column.
In the embryo, where are Hox genes expressed?
In the neural tube and somites.
What are some birth defects caused by Hox genes?
Polydactyly & synpolydactyly
Leukaemia
Cleft palate
Brain abnormalities
How are organs formed?
Tissues interact and signal to each other leading to the formation of specialised organ tissues.
How is the lung formed?
1) WNT signalling signals the lung diverticulum to grow from the gut tube.
2) Mesoderm signals FGF to endoderm which causes lung diverticulum to branch.
3) Endoderm secretes Shh back to mesoderm which causes lung bud to branch out even more.
4) Somatic mesoderm forms a vascular network around the lung bud.
What specialised cells of the lungs are formed by endoderm?
Epithelial cells and some alveolar cells.
What specialised cells of the lungs are formed by mesoderm?
Some alveolar cells (smooth muscle cells & pulmonary b.v)
