Practice question

Mammalian oocytes enter meiosis during embryonic life and become arrested in diplotene of prophase I within primordial follicles, known as dictyate stage with intact germinal vesicle nucleus and homologous chromosomes held by chiasmata. High intra-oocyte cAMP maintained by cumulus-derived signals and phosphodiesterase inhibition sustains arrest by preventing MPF activation. At birth ovaries contain approximately one million follicles dormant in this state lasting until puberty when LH surges trigger meiotic resumption. Arrest permits extensive growth, accumulation of maternal transcripts, organelles essential for early embryogenesis, zygotic reprogramming, developmental competence and embryonic viability.