Dorsal equatorial cells induce their lateral neighbors to form intermediate mesoderm. Promoters and enhancers are bound specifically by transcription factors. Trans-activating factors enable the transcription factor to interact with proteins that bind RNA polymerase. All cells of an organism contain the same mixture of transcription factors. Phylotypic Stage a.
All vertebrates are very similar to one another after organogenesis.
Among adult vertebrates, mammals remain the closest to the phylotypic organization. The phylotypic stage represents the highest stage of tolerance for variability within the ontogeny of the vertebrate body plan. Neural Plate Formation a. The neural plate is formed from chordamesoderm. Neural plate cells become columnar.