Glossary
Amnion
Is an extra-embryonic membrane which forms a fluid-filled sac that encloses and protects the embryo.
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Animal region
is the end of the egg where the nucleus resides, usually away from the yolk.
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Animal-vegital axis
This runs from the amimal pole to the vegital pole in an egg or early embryo.
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Asymmetric cell division
This is when the cell divides so that the daughter cells are different from each other because some cytoplasmic determinants have been distributed unequally between them.
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Blastocyst
A ball of about 150 cells that contains a fluid-filled cavity called a blastocoel.
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Blastomeres
These are the cells derived from cleavage of the early embryo.
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Cleavage
This occurs after fertilisation and is a series of rapid cell divisions without growth that divides the embryo up into a number of small cells.
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Cortical rotation
This occurs immediately after an amphibian egg is fertilised. The egg cortex rotates with respect to the underlying cytoplasm, toward the point of sperm entry.
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Cytoplasmic localisation
This is the non-uniform distribution of some factor or determinant in a cells cytoplasm, so that when the cell divides, the determinant is unequally distributed to the daughter cells.
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Dorsalised embryo
An embryo that is deficient in ventral regions and have much increased dorsal regions.