This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Embryology 2, Subject name: Anatomy
Concerning maturation of the female gamete (oogenesis), when do the oogonia enter meiosis I and undergo DNA replication to form primary oocytes? 
Select and explain. 
A. During fetal life, B. At bih, C. At pubey, D. With each ovarian cycle
A: During fetal life
Answer: A: During fetal life 
Explanation: All primary oocytes are formed by month 5 of fetal life, so no oogonia are present at bih. Oogonia enters meiosis I before bih. Hence at bih, ovary contains primary oocytes arrested in the diplotene stage of prophase I which gets completed after pubey to form secondary oocyte. This secondary oocyte is arrested in metaphase-2 stage of meiosis II which is completed when feilization occurs. 3rd month end 5th month 7th month Oogonia are arranged in clusters surrounded by a layer of epithelial cells. Number of germ cells in ovary reaches maximum (7 million) Majority of oocyte degenerate, except few, surviving ones enter prophase I & are surrounded by follicular epithelial cells forming PRIMORDIAL FOLLICLE.