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DB - lecture 5 - Specification of cell fates 1
Sussex University - Year 2 - Developmental Biology
13
Biology
Undergraduate 2
06/10/2013

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Term
Explain invagination.
Definition

The infolding of a region of cells, much like the indenting of a soft rubber ball when poked.

eg. sea urchin endoderm

Term
Explain involution.
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

Term
Explain ingression.
Definition

The migration of individual cells from the surface layer to the interior of the embryo.

eg. sea urchin mesoderm, and drosophila neuroblasts.

Term
Explain delamination
Definition

The splitting of one cellular sheet into two or more less parallel sheets.

eg. mammalian hypoblast

Term
Explain epiboly
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.

Term
Explain convergent extention.
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.
Term
What are the types of convergent extension during gastrulation?
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.

Term
What are some of the essential processes underlying cellular specification during gastrulation?
Definition
  • Cell proliferation
  • Cell specialization
  • Cell interaction
  • Cell movement
Term
How would we create a fate map?
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.
Term
How do we test for cell determination?
Definition
  1. Observe the normal fates of the cells
  2. 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.

Term
How did August Weismann contribute to the mosaic theory.
Definition
August Wiesmann proposed that their were nuclear determinants. these nuclear determinants segregated differently at cleavage- resulting in cells with different properties.
Term
How did Wilhelm Roux contribute to the theory of mosaic development?
Definition

Killed one cell in a two cell frog blastocel (two cell stage).

They grew into half embryos- supporting the theory.

Term
How did Hans Driesch contribute to the theory of regulative development?
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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