Question

completion of meiosis 2 in an ovum occurs in
1 birth and before puberty
2 entry of sperm in cytoplasm of ovum
3 implantation
4 degeneration of Corpus luteum​

Answer 1

$\star$ completion of meiosis 2 in an ovum occurs in

---- (2) entry of sperm in cytoplasm of ovum.

Reason:

• meiosis had been started during embryonic development and before puberty.
• They started maturing at the gain of puberty and converting the primary oocyte to secondary oocyte.
• Still they are arrested at the diplotene stage of meiosis-1 , they will complete whole cycle of meiosis-2 only after the entry of sperm.
• Which results in fertilization.
• if no fertilization occurs then, the secondary oocyte will eventually mkve from fallopian tube and goes into menstrual cycle.

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Answer 2

Answer:

Completion of meiosis 2 in an ovum occurs in entry of sperm in cytoplasm of ovum.

Explanation:

• Meiosis, a specialized two-phase cell division mechanism that generates four haploid (1N) cells from a single diploid (2N) germ cell, is how primordial germ cells develop into gametes. Crossover and DNA replication take place during meiosis I.
• Meiosis II is when centromeric division (and chromosomal number reduction) take place.
• The majority of gametogenesis in females takes place during embryonic development.
• One egg is chosen throughout a woman's reproductive cycle to go through meiosis I and develop into a secondary oocyte (1N,2C) and a first polar body.
• The oocyte is held in meiotic metaphase II after ovulation until fertilization.
• The secondary oocyte completes meiosis II during fertilization to produce a mature oocyte (23,1N) and a second polar body.

Hence, option (2) is correct.

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