At what point does the secondary oocyte complete meiosis?

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Solution

Secondary oocyte:
The primary oocyte is formed from oogonia (gamete mother cells) during oogenesis.
Primary oocytes enter prophase-I of meiosis and remain dormant till puberty. They remain arrested at this stage due to the absence of luteinizing hormone (LH).
At the onset of puberty, the primary oocyte (2n) undergoes the first meiotic division. This results in the formation of the secondary oocyte (n).
Secondary oocytes start undergoing second meiotic division but get arrested at metaphase II; until they meet the sperm in the fallopian tube.
The secondary oocyte completes meiosis at the time of fertilization. After completing meiosis, the secondary oocyte gives rise to an ovum.

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Does the sperm fuses with the ovum or the secondary oocyte?Because only after the entry of sperm secondary oocyte undergoes meiosis II and form ovum and 2nd polar body.

Q. Following statements are given w.r.t. gametogenesis.
(a) Meiosis

1^{s t}

occurs in primary oocyte
(b) Meiosis

2^{n d}

may start but can’t be completed in virgin woman’s secondary oocyte
(c) Meiosis

1^{s t}

is completed in follicular phase of menstrual cycle
(d) Meiosis

2^{n d}

produces three polar bodies and one ovum
From above

Q. Secondary oocyte which is arrested at metaphase 2 of meiosis 2 is only released during menstruation?

study the given flow chart carefully and answer the questions given below.

Oogonia------ Mitosis----- Primary Oocyte------ Meiosis I --------- Secondary Oocyte + Polar body --------Meiosis II------------- Ovum + II Polar body.

Why there is formation of polar body in Primary and Secondary oocyte after Meiosis ?

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