1. An oocyte (, oöcyte, or ovocyte) is a female germ cell involved in sexual reproduction. An oocyte is an immature ovum, an immature egg cell produced in a female fetus in the ovary during gametogenesis. During oogenesis, the oogonia become primary oocytes. An oocyte is a form of genetic material that can be collected for cryopreservation. == 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 23rd (sex) chromosome as 23,X (female-determining), whereas sperm can have 23,X (female-determining) or 23,Y (male-determining)... from wikipedia.org