Question

Oogenesis, (Write a note)

Answer 1

The process by which the eggs or ovadevelop from the primordial germ cells of the ovary is called oogenesis. The mature ovary consists of cells similar to the primordial cells in the testis. These however give rise to eggs.

The process of the development of the egg can be studied under the fol­lowing stages. These are multiplication phase, growth phase and matura­tion phase

Answer 2

Explanation:

• Oogenesis is term given to the process of formation of mature egg cells in the ovary .
• Oogenesis begins even before the female is born.
• The primitive germ cells move into the ovaries from the the yolk sac during fetal development.
• Then the germ cells differentiate and form large number of oogonia which are diploid cells.
• Oogonia then divide mitotically to produce large number of germ cells out of which many degenerated by a process called atresia.
• The few left out germ cells develop into primary oocyte that starts undergoing meiosis but is arrested at diplotene stage and remains arrested till puberty is reached.
• At puberty, the primary oocyte completes meiosis I and produces a polar body and a secondary oocyte.
• The secontary oocyte is arrested at metaphase II and the follicle around it enlarges and ruptures to release the secondary oocyte.
• If the oocyte is fertilised by a sperm then only it completes meiosis II and produces the mature ovum.