For 10 points, name this process that occurs in the early embryo, in which the blastula cleaves into three germ layers.
Mutations in Sog delay certain aspects of this process, and it occurs in a "twisted" fashion in Tsg mutants. The cerebrus protein is expressed during the early stages of this process. A group of cells important to inducing this process is activated by the Siamois transcription factor, and that group of cells was discovered using cap transplantation assays. In Xenopus, this process begins when the edge of the DIMZ rolls and bottle cells from the gray crescent invaginate to form a dorsal lip, as directed by beta-catenin and TGF-beta induced transcription of chordin and noggin in the (*) Spemann-Mangold organizer. In humans, this occurs when cells from the epiblast migrate through the primitive streak. This process forms a primitive pouch called the archenteron, which opens to the outside via the blastophore. For 10 points, name this process that occurs in the early embryo, in which the blastula cleaves into three germ layers.
Mutations in Sog delay certain aspects of this process, and it occurs in a "twisted" fashion in Tsg mutants.
gastrulation