W12 Flashcards
What is the difference between pattern forming (Musterbildung) and morphogenesis (Morphogenese- Gestaltbildung)?
Pattern forming is setting up the patterns for development. Morphogenesis changes the 3 dimensional organisation.
How are the 3D changes of morphogenesis brought about?
- Cell growth and proliferation 2. Cell death 3. Cell shape 4. Cell adhesion 5. Cell migration (plants only 1-3)
What are the 3 stages of foetus development?
- Cleavage (includes morula and blastula) 2. Gastrulation (Ectoderm, mesoderm and endoderm develop) 3. Neurulation
What are the individual egg cells at the cleavage stage?
blastomeres At this stage cleavage is not accompanied by cell growth, because the egg cell is already big. This enables very fast division.
What happens with very yolky eggs in the cleavage stage?
Cytokinesis during the cleavage cycle is either incomplete (zebra fish, chicken) or doesn’t occur (D. malanogaster)
Stages of cleavage in Drosophila.
- 30 min - fusion of sperm and egg nuclei 2. 70 min - nuclear division creating syncytium 3. 90 min - nuclei migrate to periphery of cytoplasm 4. 2h - syncytial blastoderm 5. 3h - cellular blastoderm
Why is the axis of cell division important?
- control tissue outgrowth 2. control asymmetric cell division e.g. C. elegans. AB and P1 cells divide along different axes.
What is a mammalian embryo at the blastula stage called and what are its components?
Blastocyst 1. inner cell mass (becomes animal) 2. blastocoel 3. trophectoderm (becomes placenta)
What are the morphogenetic processes and mechanisms of blastocyst formation?
Processes: compaction (morula), blastocoel formation Mechanisms: cell adhesion, cell polarization, oriented cell division
How does compaction occur?
By minimizing the cell surface not touching another cell. This affects cell polarity as well, the outer apical cell surface being different from the basolateral surface.
What are the two types of cleavage of a polarized cell, and what are their effects?
- radial cleavage - 2 polarized cells 2. tangential cleavage - 1 polarized cell, 1 nonpolarized cell
What is the effect of cell polarization in the formation of the blastocyte?
Sodium ions are transported more towards the inside, increasing the hydrostatic pressure, generates blastocoel. 2. tangential cleavage in one region generates inner cell mass.
What are the molecular mechanisms of cell adhesion?
- cell-cell adhesion: cadherins (Ca2+ dependent), immunoglobulin super family proteins (e.g. N-CAM: neural cell adhesion molecule) 2. cell-matrix adhesion: integrins (transmembrane proteins) - laminin (protein of extracellular matrix)
What is the important cell adhesion factor for the development of morula?
E-cadherin
What is the cause of the phenomenon seen in the sorting out experiment?
Different cell types have distinct cell adhesion characteristics. This allowed the identification of cell adhesion molecules.