This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
After first meiotic division, the primary oocyte remains arrested in ? 
Select and explain. 
A. Diplotene stage, B. Pachytene stage, C. Metaphase, D. Telophase
A: Diplotene stage
Answer: A: Diplotene stage 
Explanation: Ans. is 'a' i.e., Diplotene stage Oogenesis refers to the process of formation of ova from the primitive germ cells. Unlike fetal testis (in which spermatogenesis beings at pubey), the fetal ovary begins oogenesis by 10 weeks of gestation. The sequence of events in oogenesis are : The primitive germ cells undergo mitotic divisions to form oogonia (diploid cells). Oogonium is unique in that it is the only female cell in which both X' chromosomes are active. The oogonia proliferate by mitosis to form primary oocytes (diploid cells). Primary oocytes formed from the oogonia enter a prolonged prophase (diplotene stage) of the first meiotic division and remain in this stage until ovulation occurs after pubey. Primary oocytes completes the first meiotic division at pubey just before ovulation to form secondary oocyte (haploid cell) and 1st polor body. Secondary oocyte immediately begins second meiotic division but this division stops at metaphase and is completed only if the mature ovum (ootid) is feilized with sperm. At that time second polor body (polocyte) is extruded and the feilized ovum proceeds to form a new individual. Feilization normally occurs in the ampulla of fallopian tube.