Question

Secondary oocyte is released from the ovary at which stage?

• A. Completion of meiosis I and meiosis II
• B. After meiosis I followed by mitosis
• C. After meiosis I before the start of meiosis II
• D. Meiosis I before completion of meiosis II

Answer 1

The correct option is D Meiosis I before completion of meiosis II

Female gametes are formed by oogenesis. Oogenesis involves three phases, they are the multiplication phase, growth phase and maturation phase. The multiplication phase occurs in the foetal ovary where the oogonia are converted into primary oocytes that are arrested in the diplotene stage of prophase I. The growth phase occurs once the female attains puberty. In this phase, the primary oocytes enlarge in size. In the maturation phase, the primary oocyte(2n) undergoes meiosis I to form one haploid secondary oocyte (n) and a tiny first polar body (n). The secondary oocyte is released after completing meiosis I and before the completion of meiosis II (they are arrested in the metaphase stage). When the Graafian follicle (mature follicle) ruptures, it releases secondary oocyte arrested in the metaphase stage of meiotic II from the ovary by the process called ovulation. This secondary oocyte completes its meiosis II upon sperm entry.