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Definition
The infolding of a region of cells, much like the indenting of a soft rubber ball when poked.
eg. sea urchin endoderm |
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Definition
The inturning or inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells
eg. amphibian mesoderm |
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Definition
The migration of individual cells from the surface layer to the interior of the embryo.
eg. sea urchin mesoderm, and drosophila neuroblasts. |
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Definition
The splitting of one cellular sheet into two or more less parallel sheets.
eg. mammalian hypoblast |
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Definition
The movement of epithelial sheets that spread as a unit, rather than individually, to enclose the deeper layers of the embryo
eg. ectoderm formation in amphibians, sea urchins, tunicates. |
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Term
| Explain convergent extention. |
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Definition
| Mechanism for elongating a sheet of cells in one direction while narrowing its width, and occurs by rearrangement of cells within the sheet, rather than by cell migration or cell division. |
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Term
| What are the types of convergent extension during gastrulation? |
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Definition
Intercalation is when cells elongate at the ends and shuffle in between eachother.
Medio-lateral interacalation- along the medio-lateral axis, resulting in a longer, narrower row of cells.
Radical intercalation- perpendicular to the surface, thinning it and expanding it. |
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Term
| What are some of the essential processes underlying cellular specification during gastrulation? |
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Definition
- Cell proliferation
- Cell specialization
- Cell interaction
- Cell movement
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Term
| How would we create a fate map? |
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Definition
| By injecting dye into cells and tracking their movements to find out which cells end up where. They don't revel the states of cellular determination though. |
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Term
| How do we test for cell determination? |
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Definition
- Observe the normal fates of the cells
- Transplant a section from an embryo onto a different section on a different embryo of the same species.
If the cells follow their original specification fate in spite of the transplantation they are determined. |
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Term
| How did August Weismann contribute to the mosaic theory. |
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Definition
| August Wiesmann proposed that their were nuclear determinants. these nuclear determinants segregated differently at cleavage- resulting in cells with different properties. |
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Term
| How did Wilhelm Roux contribute to the theory of mosaic development? |
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Definition
Killed one cell in a two cell frog blastocel (two cell stage).
They grew into half embryos- supporting the theory. |
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Term
| How did Hans Driesch contribute to the theory of regulative development? |
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Definition
| He separated the two cells form the blastocel of an early sea urchin embryo. The separation resulted in the death of one cell and the surviving cell developed into a small but otherwise normal larva. |
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