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Question
Oogenesis involves
Oogenesis involves
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Solution
The correct option is C All of the above
Oogenesis is the creation of an ovum (egg cell). It is the female form of gametogenesis. It involves the development of the various stages of the immature ovum. It consists of three phases: multiplication, growth and maturation.Multiplication Phase: In the foetal development, certain cells in the germinal epithelium of the ovary of the foetus are larger than others. These cells divide by mitosis, producing a couple of million egg mother cells or oogonia in each ovary of the foetus. The oogonia multiplied by mitotic divisions forming the primary oocytes.Growth Phase: This phase of the primary oocyte is very long. It may extend over many years. The oogonium grows into a large primary oocytes. Each primary oocyte then gets surrounded by a layer of granulosa cells to form primary follicle. A large number of these follicles degenerate during the period from birth to puberty. So at puberty only 60,000- 80,000 primary follicles are left in each ovary.Maturation Phase: Like a primary spermatocyte, each primary oocyte undergoes two maturation divisions, first meiotic and the second meiotic.In the first, meiotic division, the primary oocyte divides into two very unequal haploid daughter cells, a large secondary oocyte and a very small first polar body. In the second maturation division, the first polar body may divide to form two second polar bodies. The secondary oocyte again divides into unequal daughter cells, a large ootid and a very small second polar body. The ootid grows into a functional haploid ovum. Thus, from one oogonium, one ovum, and three polar bodies are formed. The ovum is the actual female gamete. The polar bodies take no part in reproduction and hence, soon degenerate. In human beings, an ovum is released from the ovary in the secondary oocyte stage. The maturation of secondary oocyte is completed in the mother’s oviduct (fallopian tube). Thus, the correct answer is option D.
Oogenesis is the creation of an ovum (egg cell). It is the female form of gametogenesis. It involves the development of the various stages of the immature ovum. It consists of three phases: multiplication, growth and maturation.
Multiplication Phase: In the foetal development, certain cells in the germinal epithelium of the ovary of the foetus are larger than others. These cells divide by mitosis, producing a couple of million egg mother cells or oogonia in each ovary of the foetus. The oogonia multiplied by mitotic divisions forming the primary oocytes.
Growth Phase: This phase of the primary oocyte is very long. It may extend over many years. The oogonium grows into a large primary oocytes. Each primary oocyte then gets surrounded by a layer of granulosa cells to form primary follicle. A large number of these follicles degenerate during the period from birth to puberty. So at puberty only 60,000- 80,000 primary follicles are left in each ovary.
Maturation Phase: Like a primary spermatocyte, each primary oocyte undergoes two maturation divisions, first meiotic and the second meiotic.In the first, meiotic division, the primary oocyte divides into two very unequal haploid daughter cells, a large secondary oocyte and a very small first polar body. In the second maturation division, the first polar body may divide to form two second polar bodies. The secondary oocyte again divides into unequal daughter cells, a large ootid and a very small second polar body. The ootid grows into a functional haploid ovum. Thus, from one oogonium, one ovum, and three polar bodies are formed. The ovum is the actual female gamete. The polar bodies take no part in reproduction and hence, soon degenerate. In human beings, an ovum is released from the ovary in the secondary oocyte stage. The maturation of secondary oocyte is completed in the mother’s oviduct (fallopian tube). Thus, the correct answer is option D.
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