Oocyte

[3] The cumulus-oocyte complex contains layers of tightly packed cumulus cells surrounding the oocyte in the Graafian follicle.

[4][5][6] In order for an oocyte to become fertilized and ultimately grow into a fully functioning organism, it must be able to regulate multiple cellular and developmental processes.

The DNA of a cell is vulnerable to the damaging effect of oxidative free radicals produced as byproducts of cellular metabolism.

DNA damage occurring in oocytes, if not repaired, can be lethal and result in reduced fecundity and loss of potential progeny.

[7][8] Thus, oocytes of many organisms are protected from oxidative DNA damage while storing up a large mass of substances to nurture the zygote in its initial embryonic growth.

In certain organisms, such as mammals, paternal mitochondria brought to the oocyte by the spermatozoon are degraded through the attachment of ubiquitinated proteins.

[22] Maternal cells also synthesize and contribute a store of ribosomes that are required for the translation of proteins before the zygotic genome is activated.

In mammalian oocytes, maternally derived ribosomes and some mRNAs are stored in a structure called cytoplasmic lattices.

These cytoplasmic lattices, a network of fibrils, protein, and RNAs, have been observed to increase in density as the number of ribosomes decrease within a growing oocyte[23] and mutation in them have been linked to infertility.

The arrest of ooctyes at the four genome copy stage appears to provide the informational redundancy needed to repair damage in the DNA of the germline.

[29] DNA repair capability appears to be a key quality control mechanism in the female germ line and a critical determinant of fertility.