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Thus it appears that a process evolved to avoid this vulnerability of germline DNA. It was proposed that, in order to avoid damage to the DNA genome of the oocytes, the metabolism contributing to the synthesis of much of the oocyte's constituents was shifted to other maternal cells that then transferred these constituents to oocytes.
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.
In humans and other mammals, DNA damage occurs frequently and DNA repair processes have evolved to compensate. [11] In estimates made for mice, DNA lesions occur on average 25 to 115 times per minute in each cell, or about 36,000 to 160,000 per cell per day. [12] Some DNA damage may remain in any cell despite the action of repair processes.
In mammalian females the period of arrest may last for years. During this period of arrest, oocytes are subject to spontaneous DNA damage including double-strand breaks. However, the oocytes can efficiently repair DNA double-strand breaks, allowing the restoration of genetic integrity and the protection of offspring health. [8]
However, homologous recombinational repair of DNA double-strand breaks mediated by BRCA1 and ATM weakens with age in oocytes of humans and other species. [25] Women with BRCA1 mutations have lower ovarian reserves and experience earlier menopause than women without these mutations. Even in woman without specific BRCA1 mutations, ovarian aging ...
Bile acids cause DNA damage, including oxidative DNA damage, double-strand DNA breaks, aneuploidy and chromosome breakage. [55] High-normal levels of the bile acid deoxycholic acid cause apoptosis in human colon cells, [ 56 ] but may also lead to colon cancer if repair and apoptotic defenses are insufficient.
The peer-reviewed research from Harvard Medical School found that DEET had negative impacts on the reproductive systems of Caenorhabditis elegans, a species of worm with genetic similarities to ...
Oocytes (female germ cells) located in the primordial follicle of the ovary are in a non-growing prophase arrested state, but are able to undergo highly efficient homologous recombinational repair of DNA damages including double-strand breaks. [8] This capability allows the maintenance of genome integrity and protection of the health of ...