Answer: Oogenesis is the process by which ovum mother cells or oogonia gives rise to mature ovum- the female gametes. The process takes place in the outermost layer- the germinal epithelium of the ovary. Meiotic Events in oogenesis: Initially before birth, the oogonium undergoes mitotic divisions so as to increase its number. This process takes place during the embryonic growth phase. No further addition to this number takes place after birth. In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells. After the seventh month though, there is a sharp decline in the number of these newly formed cells. These remaining cells are the ones entering the reductional division of meiosis (meiosis-1). These cells enters into meiosis-1 but they are unable to advance through Prophase-1 of meiosis. These cells are arrested in the diplotene sub-stage of Prophase-1 and they are maintained at this stage until puberty. These cells are now known as primary oocytes. Even the primary oocytes continue to die during this phase. Roughly only about 400 oocytes mature during the reproductive life of a female periodically. At the onset of puberty, specific hormonal cues re-initiate the process of meiosis. During adolescence, the GnRH or gonadotropin releasing hormones released from the hypothalamus signals the anterior pituitary to release hormones like LH & FSH which lifts the cell cycle arrest in these cells and assists them in resuming meiosis. The primary oocytes completes meiosis-1 and gives rise to a tiny polar body and another larger secondary oocyte with greater content of cytoplasm ( unequal cell division). In some organisms , the polar bodies may again divide to form 2 polar bodies while it dies off in case of humans. The secondary oocyte thus produced advances through Meiosis-2 ( equational division) but halts at meiosis-2. The secondary oocyte is released from the follicle and it travels towards the fallopian tube. The immature secondary oocyte can re-enter cell cycle and complete the remaining sub-stages of meiosis-2 only if union with a sperm takes place. The secondary oocyte progresses through meiosis-2 giving rise to another polar body and a female pro-nucleus which unites with the sperm and gives rise to the zygote or the fertilized egg. Thus begins the process of embryonic development. Developmental process in oogenesis: Oogonia are formed from the primoridial germ cells of the ovary by mitotic cell division. By growth & maturation oogonia increase in size and become primary oocytes. During this phase, synthesis of food and factors required for further differentiation are synthesized. During the growth phase, the primary oocytes gets surrounded by specialized cells of the ovary known as follicle cells. Once they are fully formed, cavities are formed and these gets filled with their own secretion. At this stage, it is known as Graafian follicle. Oocyte collects .

1. Answer:
Oogenesis is the process by which ovum mother cells or oogonia gives rise to mature ovum- the
female gametes. The process takes place in the outermost layer- the germinal epithelium of the
ovary.
Meiotic Events in oogenesis:
Initially before birth, the oogonium undergoes mitotic divisions so as to increase its number. This
process takes place during the embryonic growth phase. No further addition to this number takes
place after birth. In the human embryo, the thousand or so oogonia divide rapidly from the
second to the seventh month of gestation to form roughly 7 million germ cells. After the seventh
month though, there is a sharp decline in the number of these newly formed cells. These
remaining cells are the ones entering the reductional division of meiosis (meiosis-1). These cells
enters into meiosis-1 but they are unable to advance through Prophase-1 of meiosis. These cells
are arrested in the diplotene sub-stage of Prophase-1 and they are maintained at this stage until
puberty. These cells are now known as primary oocytes. Even the primary oocytes continue to
die during this phase. Roughly only about 400 oocytes mature during the reproductive life of a
female periodically. At the onset of puberty, specific hormonal cues re-initiate the process of
meiosis.
During adolescence, the GnRH or gonadotropin releasing hormones released from the
hypothalamus signals the anterior pituitary to release hormones like LH & FSH which lifts the
cell cycle arrest in these cells and assists them in resuming meiosis. The primary oocytes
completes meiosis-1 and gives rise to a tiny polar body and another larger secondary oocyte with
greater content of cytoplasm ( unequal cell division). In some organisms , the polar bodies may
again divide to form 2 polar bodies while it dies off in case of humans. The secondary oocyte
thus produced advances through Meiosis-2 ( equational division) but halts at meiosis-2. The
secondary oocyte is released from the follicle and it travels towards the fallopian tube. The
immature secondary oocyte can re-enter cell cycle and complete the remaining sub-stages of
meiosis-2 only if union with a sperm takes place. The secondary oocyte progresses through
meiosis-2 giving rise to another polar body and a female pro-nucleus which unites with the
sperm and gives rise to the zygote or the fertilized egg. Thus begins the process of embryonic
development.
Developmental process in oogenesis:
Oogonia are formed from the primoridial germ cells of the ovary by mitotic cell division. By
growth & maturation oogonia increase in size and become primary oocytes. During this phase,
synthesis of food and factors required for further differentiation are synthesized. During the
growth phase, the primary oocytes gets surrounded by specialized cells of the ovary known as

2. follicle cells. Once they are fully formed, cavities are formed and these gets filled with their own
secretion. At this stage, it is known as Graafian follicle. Oocyte collects its nutrition through
zona radiata. After maturation, a membrane appears in the oocytce known as primary egg
membrane. During this phase, there is also an increase in nuclear size & lampbrush
chromosomes are observed. mRNA synthesis increases substantially along with a quantitative
increase in cytoplasm.
After growth is completed, at puberty the primary oocytes undergo meiosis-1 and gives rise to
secondary oocytes contained within the secondary follicle. Secondary oocyte and first polar body
are released just before onset of ovulation. The polar body degenerates and dies off. The
secondary oocyte released at ovulation is surrounded by the zona pellucida and a follicular cell
layer, the corona radiata. The graafian follicle which releases the secondary oocyte is now known
as the corpus luteum and it secretes progesterone. The secondary oocyte is the immature ovum
which enters into meiosis-2. If the secondary oocyte meets the sperm, it forms the ootid which
again gives rise to mature ovum.
FSH plays an active role in the maturation of ovarian follicle, it helps in its differentiation giving
rise to structures like antrum, zona pellucida etc. But for the final maturity, LH is essential.
When LH surge occurs, the secondary oocyte is released from the follicle
Solution
Answer:
Oogenesis is the process by which ovum mother cells or oogonia gives rise to mature ovum- the
female gametes. The process takes place in the outermost layer- the germinal epithelium of the
ovary.
Meiotic Events in oogenesis:
Initially before birth, the oogonium undergoes mitotic divisions so as to increase its number. This
process takes place during the embryonic growth phase. No further addition to this number takes
place after birth. In the human embryo, the thousand or so oogonia divide rapidly from the
second to the seventh month of gestation to form roughly 7 million germ cells. After the seventh
month though, there is a sharp decline in the number of these newly formed cells. These
remaining cells are the ones entering the reductional division of meiosis (meiosis-1). These cells
enters into meiosis-1 but they are unable to advance through Prophase-1 of meiosis. These cells
are arrested in the diplotene sub-stage of Prophase-1 and they are maintained at this stage until
puberty. These cells are now known as primary oocytes. Even the primary oocytes continue to
die during this phase. Roughly only about 400 oocytes mature during the reproductive life of a
female periodically. At the onset of puberty, specific hormonal cues re-initiate the process of

3. meiosis.
During adolescence, the GnRH or gonadotropin releasing hormones released from the
hypothalamus signals the anterior pituitary to release hormones like LH & FSH which lifts the
cell cycle arrest in these cells and assists them in resuming meiosis. The primary oocytes
completes meiosis-1 and gives rise to a tiny polar body and another larger secondary oocyte with
greater content of cytoplasm ( unequal cell division). In some organisms , the polar bodies may
again divide to form 2 polar bodies while it dies off in case of humans. The secondary oocyte
thus produced advances through Meiosis-2 ( equational division) but halts at meiosis-2. The
secondary oocyte is released from the follicle and it travels towards the fallopian tube. The
immature secondary oocyte can re-enter cell cycle and complete the remaining sub-stages of
meiosis-2 only if union with a sperm takes place. The secondary oocyte progresses through
meiosis-2 giving rise to another polar body and a female pro-nucleus which unites with the
sperm and gives rise to the zygote or the fertilized egg. Thus begins the process of embryonic
development.
Developmental process in oogenesis:
Oogonia are formed from the primoridial germ cells of the ovary by mitotic cell division. By
growth & maturation oogonia increase in size and become primary oocytes. During this phase,
synthesis of food and factors required for further differentiation are synthesized. During the
growth phase, the primary oocytes gets surrounded by specialized cells of the ovary known as
follicle cells. Once they are fully formed, cavities are formed and these gets filled with their own
secretion. At this stage, it is known as Graafian follicle. Oocyte collects its nutrition through
zona radiata. After maturation, a membrane appears in the oocytce known as primary egg
membrane. During this phase, there is also an increase in nuclear size & lampbrush
chromosomes are observed. mRNA synthesis increases substantially along with a quantitative
increase in cytoplasm.
After growth is completed, at puberty the primary oocytes undergo meiosis-1 and gives rise to
secondary oocytes contained within the secondary follicle. Secondary oocyte and first polar body
are released just before onset of ovulation. The polar body degenerates and dies off. The
secondary oocyte released at ovulation is surrounded by the zona pellucida and a follicular cell
layer, the corona radiata. The graafian follicle which releases the secondary oocyte is now known
as the corpus luteum and it secretes progesterone. The secondary oocyte is the immature ovum
which enters into meiosis-2. If the secondary oocyte meets the sperm, it forms the ootid which
again gives rise to mature ovum.
FSH plays an active role in the maturation of ovarian follicle, it helps in its differentiation giving
rise to structures like antrum, zona pellucida etc. But for the final maturity, LH is essential.
When LH surge occurs, the secondary oocyte is released from the follicle