ABSTRACT
The oocyte provides all proteins, especially transcription factors, mRNA, tRNA, and ribosomal RNA, as well as cell organelles like mitochondria to support the first mitotic divisions and early embryogenesis. It has to provide for initiation of zygotic gene activation until full zygotic gene expression is achieved. All the information obtained by genetic models and observations on correlations between oocyte quality and developmental competence in assisted reproduction thus support the notion that embryogenesis is governed by and begins during oogenesis22,23 and is dependent on timed expression during oogenesis. The continued development and maturation of the oocyte within the ovarian follicle in vivo facilitates the production of oocytes of the highest developmental potential. Up to now, invitro conditions do not fully support the process of oocyte growth and maturation as effectively. This may relate to deficiencies in the extracellular milieu, or result from the suboptimal quality of the oocyte at the beginning of and during culture, especially in primates (e.g. reference 24).
