They are highly conserved and have been found in animals as diverse as insects and humans. They encode transcription activators. They direct gastrulation. A mutation is a Drosophila segmentation gene is most likely to a. change the number of larval segments. Regulated gene expression is very important.
Gastrulation occurs before organogenesis.
The process which involves cell movement and by which three different tissue precursors are created is a. neurulation. The initial stages of insect development are regulated by a. paternal genes. The initial period of cell division during which the blastula forms from the zygote is called a. cleavage. The fundamental question of importance to developmental biology that was addressed with the Dolly experiment is a. Gastrulation in birds and frogs differs considerably.