Oogenesis is the process of meiosis in female organisms from an oogonium to a primary oocyte, to a secondary oocyte, and then to an ovum.
The gamete formed by oogenesis contains all the materials needed to initiate and maintain metabolism and development of the embryo outside the mothers body.
Therefore, in addition to forming a haploid nucleus, oogenesis also builds up a store of cytoplasmic enzymes, mRNAs, organelles, and metabolic substrates.
During the first division of Oogenic meiosis, unequal cytokinesis take place and result in one of the two daughter cells containing hardly any cytoplasm, whereas the other cell has nearly the entire volume of cellular constituents.
The smaller cell is called the first polar body, and the larger cell is called as the secondary oocyte.
During the second division of meiosis, a similar unequal cytokinesis takes place in secondary oocyte and result in o ne large cell (ovum), and a small cell (second polar body) .
The polar bodies receive the same chromosome complement as the secondary oocyte and ovum, but are not functional sex cells.
Because of accumulation of nutrient materials, an egg is usually much larger than a sperm of the same species.
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