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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 ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 19 December 2024. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself is produced by fusion of two gametes, each having been produced by meiotic cell division. [5] [6] After growth from the zygote to the adult, cell division by mitosis allows for continual construction and repair of the organism. [7]
The embryo forms a disc of cells, called a blasto-disc, on top of the yolk. Discoidal cleavage is commonly found in monotremes, birds, reptiles, and fish that have telolecithal egg cells (egg cells with the yolk concentrated at one end). The layer of cells that have incompletely divided and are in contact with the yolk are called the "syncytial ...
The three cells left at the end of the cell near the micropylar become the egg apparatus with an egg cell in the center and two synergids. A cell wall forms around the other set of nuclei and forms the antipodals. The cells in the center develop into the central cell. This entire structure with its eight nuclei is called the embryonic sac.
It is characterised by the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a one-celled zygote to an adult human being. Fertilization occurs when the sperm cell successfully enters and fuses with an egg cell . [2]
Oocyte abnormalities can be caused by a variety of genetic factors affecting different stages in meiosis. [1] Moreover, ageing is associated with oocyte abnormalities since higher maternal age is associated with oocytes with a reduced gene expression of spindle assembly checkpoints which are important in maintaining stability in the genome.
Mitosis is the normal process in eukaryotes for cell division; duplicating chromosomes and segregating one of the two copies into each of the two daughter cells, in contrast with meiosis. The mitosis theory states that meiosis evolved from mitosis. [ 9 ]