Mechanisms Regulating Pattern Formation in the Amphibian Egg and Early Embryo

  • J. C. Gerhart
Part of the Biological Regulation and Development book series (BRD, volume 2)


Interest in pattern regulation arose with the first experiments of embryology almost a century ago. The hypotheses of His and Weismann (reviewed by Wilson, 1896) predicted that the fertilized egg behaves as a mosaic of autonomously differentiating parts, due to either the invisible promorphology of its cytoplasm (His) or the preexisting architecture of its chromosomes (Weismann). Roux’s first experiments in 1888 seemed to support these hypotheses: he pricked a frog egg (Rana esculenta) at the two-cell stage with a hot needle so as to inactivate one cell, hence half the egg, and found the other cell continuing to divide and in many cases developing into a half-embryo, usually a right or left half. Thus, the active cell failed to adjust its development to compensate for its defective neighbor, at least under these experimental conditions. The frog egg appeared to meet the definition of a mosaic egg, that is, one showing no pattern regulation.


Germinal Vesicle Yolk Mass Maturation Promote Factor Late Blastula Animal Hemisphere 
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Copyright information

© Springer Science+Business Media New York 1980

Authors and Affiliations

  • J. C. Gerhart
    • 1
  1. 1.Department of Molecular BiologyUniversity of CaliforniaBerkeleyUSA

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