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An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis ...
Oogenesis starts with the process of developing primary oocytes, which occurs via the transformation of oogonia into primary oocytes, a process called oocytogenesis. [11] From one single oogonium, only one mature oocyte will rise, with 3 other cells called polar bodies. Oocytogenesis is complete either before or shortly after birth.
The development and maturation of sex cells also takes place during meiosis. Gametogenesis is also the process of formation in male and female gametes that occur in the gonads (ovary and testis). Both male and female produce gametes. Male gametocytes are called spermatocytes and female gametocytes are called oocytes.
Mitotic germ stem cells, oogonia, divide by mitosis to produce primary oocytes committed to meiosis. Unlike sperm production, oocyte production is not continuous. These primary oocytes begin meiosis but pause in diplotene of meiosis I while in the embryo. All of the oogonia and many primary oocytes die before birth.
However, each chromosome still has two chromatids, making a total of 46 chromatids (1N but 2C). The secondary oocyte continues the second stage of meiosis (meiosis II), and the daughter cells are one ootid and one polar body. Secondary oocytes are the immature ovum shortly after ovulation, to fertilization, where it turns into an ootid. Thus ...
The anterior end of the egg becomes the head; posterior end becomes the tail. the dorsal side is on the top; the ventral side is in underneath. The products of maternal effect genes called maternal mRNAs are produced by nurse cell and follicle cells and deposited in the egg cells (oocytes).
Gametes are produced by the haploid generation, which is known as the gametophyte. The female gametophyte produces structures called archegonia, and the egg cells form within them via mitosis. The typical bryophyte archegonium consists of a long neck with a wider base containing the egg cell. Upon maturation, the neck opens to allow sperm cells ...
Ovarian stem cells are oocytes formed in ovarian follicle before birth in female mammals. They do not form post-natally , and are depleted throughout reproductive life. [ 1 ] In humans it is estimated that 500,000–1,000,000 primordial follicles are present at birth, decreasing rapidly with age until roughly age 51 when ovulation stops ...