Biology Class 12 NCERT Solutions: Chapter 3 Human Reproduction Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 12 What is oogenesis? Give a brief account of oogenesis.

Answer:

  • Oogenesis is the process of the formation of a mature ovum from the oogonia in females. It takes place in the ovaries.
  • During oogenesis, a diploid oogonium or egg mother cell increases in size and gets transformed into a diploid primary oocyte.
  • This diploid primary oocyte undergoes first meiotic division i.e.. , meiosis I or reductional division to form two unequal haploid cells.
  • The smaller cell is known as the first polar body, while the larger cell is known as the secondary oocyte.
  • This secondary oocyte undergoes second meiotic division i.e.. , meiosis II or equational division and gives rise to a second polar body and an ovum.
  • Hence, in the process of oogenesis, a diploid oogonium produces a single haploid ovum while two or three polar bodies are produced.
Process of Oogenesis

Q. 13 Draw a labeled diagram of a section through ovary.

Answer:

Normal Ovary

Q. 14 Draw a labeled diagram of a Graafian Follicle?

Answer:

Graafian Follicle

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