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Entwicklung der

Entwicklung der Polarität side view of an egg photographed just before fertilization -> asymmetric distribution of molecules inside the egg -> fertilization defines a dorsoventral as well as an animal-vegetal asymmetry -> Vg1 codes for a member of the TGFβ protein superfamily -> fertilization triggers two types of intracellular movement (microtubules) -> rotation of the egg cortex (a layer a few µm deep) through about 30° relative to the core of the egg in a direction determined by the site of sperm entry -> active transport of dishevelled (Dsh) protein toward the future dorsal side -> dorsal concentration of dishevelled protein defines the dorsoventral polarity Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002 Biologie für Physikerinnen und Physiker Kapitel VI Entwicklung 12

Blastula Stadium rapid subdivision of the egg into many smaller cells cells divide synchronously for the first 12 cleavages, but the divisions are asymmetric lower, vegetal cells, encumbered with yolk, are fewer and larger Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002 Biologie für Physikerinnen und Physiker Kapitel VI Entwicklung 13