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Oocyte Maturation Inhibitor
The oocyte maturation inhibitor (OMI) is an inhibitory factor created by follicular cells during a primary oocyte maturation. It is believed to be the reason why the oocyte remains for so long in the immature dictyate state of meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r .... References {{reflist Embryology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Oocyte
An oocyte (, ), 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, forming oogonia. During oogenesis, the oogonia become primary oocytes. An oocyte is a form of genetic material that can be collected for cryoconservation. Formation The formation of an oocyte is called oocytogenesis, which is a part of oogenesis. Oogenesis results in the formation of both primary oocytes during fetal period, and of secondary oocytes after it as part of ovulation. Characteristics Cytoplasm Oocytes are rich in cytoplasm, which contains yolk granules to nourish the cell early in development. Nucleus During the primary oocyte stage of oogenesis, the nucleus is called a germinal vesicle. The only normal human type of secondary oocyte has the 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dictyate
The dictyate or dictyoteneMedical Physiology, Boron & Boulpaep, , Elsevier Saunders 2005. Updated edition. 1300 pages. is a prolonged resting phase in oogenesis. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation by the LH surge. Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the dictyate stage until puberty commences and the cells complete ootidogenesis. In both mouse and human, oocyte DNA of older individuals has substantially more double-strand breaks than that of younger individuals.{{cite journal , vauthors=Titus S, Li F, Stobezki R, Akula K, Unsal E, Jeong K, Dickler M, Robson M, Moy F, Goswami S, Oktay K , title=Impairment of BRCA1-related DNA double-strand break repair leads to ovarian aging in mice and humans , journal=Sci Transl Med , volume=5 , issue=172 , pages=172ra21 , year=2013 , pmid=23408054 , doi=10.1126/scitra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately result in four cells with only one copy of each chromosome ( haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and female will fuse to create a cell with two copies of each chromosome again, the zygote. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
