Final answer:
Cytoplasmic rearrangements in the fertilized egg of the tunicate Styela partita are induced by differential gene expression, which guides cellular processes for embryonic development, similar to the role of maturation promoting factor (MPF) in Xenopus eggs.
Step-by-step explanation:
Cytoplasmic rearrangements in the fertilized egg of the tunicate Styela partita are induced by differential gene expression. During the early embryonic development, after fertilization, the gametes fuse to form a zygote. As this zygote begins to develop, the genetic material starts to direct various cellular processes that lead to the rearrangement of the cytoplasm, creating an organized structure necessary for further development. An example of such regulation is seen in Xenopus eggs, where the maturation promoting factor (MPF) present in cytoplasm of mid-meiotic cells can induce meiosis when injected into pre-meiotic cells. MPF illustrates how specific substances within the cytoplasm can control cell cycle and development in early embryos. Similarly, the process in the tunicate likely involves factors that control the reorganization of cellular material to form structures such as the trophoblast and inner cell mass in mammals, which then give rise to the blastocyst.