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DNA damage occurring in oocytes, if not repaired, can be lethal and result in reduced fecundity and loss of potential progeny. Oocytes are substantially larger than the average somatic cell, and thus considerable metabolic activity is necessary for their provisioning.
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.
When there is too much damage, apoptosis is triggered in order to protect the organism from potentially harmful cells.7 p53, also known as a tumor suppressor gene, is a major regulatory protein in the DNA damage response system which binds directly to the promoters of its target genes. p53 acts primarily at the G1 checkpoint (controlling the G1 ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 11 February 2025. 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 ...
In human cells, oxidative DNA damage occurs about 10,000 times a day and DNA double-strand breaks occur about 10 to 50 times a cell cycle in somatic replicating cells (see DNA damage (naturally occurring)). The selective advantage of DNA repair is to allow the cell to survive in the face of DNA damage.
Germ cell tumors are generally located in the gonads but can also appear in the abdomen, pelvis, mediastinum, or brain. Germ cells migrating to the gonads may not reach that intended destination and a tumor can grow wherever they end up, but the exact cause is still unknown. These tumors can be benign or malignant. [23]
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. [4]
As reviewed by Howell et al., [8] DNMT1o is sequestered in the cytoplasm of mature oocytes and in 2-cell and 4-cell embryos, but at the 8-cell stage is only present in the nucleus. At the 16 cell stage (the morula) DNMT1o is again found only in the cytoplasm. It appears that demethylation of the maternal chromosomes largely takes place by ...