During oogenesis dramatic changes take place within the oocyte. These include changes in the size, yolk content and distribution, meiotic state of the oocyte, as well as progressive changes in the distribution of maternally supplied mRNAs and proteins that are required for development following fertilization. The morph sequence at the right illustrates the enormous changes in external appearance of the Xenopus oocyte as it progresses through oogenesis.
A morph sequence of successive stages during Xenopus oogenesis