Arrange the following structures involved in oogenesis in correct seq…

The correct answer is Option (2) → (D), (C), (A), (B)

(D) Oogonia — first. Oogenesis starts before birth. During embryonic development, a couple of million gamete mother cells (oogonia) form in each foetal ovary. No more oogonia are added after birth.

(C) Primary oocyte — second. The oogonia enter the first meiotic division and stop at prophase-I. These arrested cells are the primary oocytes.

(A) Secondary oocyte — third. Inside the tertiary follicle, the primary oocyte completes the first meiotic division. The division is unequal. It gives a large haploid secondary oocyte and a tiny first polar body. The secondary oocyte is released at ovulation.

(B) Ovum — last. The second meiotic division is completed only when a sperm enters the secondary oocyte. It again divides unequally and forms the haploid ovum (ootid) and a second polar body.

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NCERT Extract:
Gametogenesis – “… Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary; no more oogonia are formed and added after birth. These cells start division and enter into prophase-I of the meiotic division and get temporarily arrested at that stage, called primary oocytes.”