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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.
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. [26] The repair process used likely involves homologous recombinational repair. [26] [27] [28] Prophase arrested oocytes have a high capability for efficient repair of DNA damages. [27]
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]
Most of the DNA repair deficiency diseases show varying degrees of "accelerated aging" or cancer (often some of both). [37] But elimination of any gene essential for base excision repair kills the embryo—it is too lethal to display symptoms (much less symptoms of cancer or "accelerated aging"). [38]
BRCA1 and ATM proteins are employed in repair of DNA double-strand break during meiosis. These proteins appear to have a critical role in resisting ovarian aging. [25] 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]
The dictyate appears to be an adaptation for efficiently removing damages in germ line DNA by homologous recombinational repair. [5] Prophase arrested oocytes have a high capability for efficient repair of DNA damages. [5] DNA repair capability appears to be a key quality control mechanism in the female germ line and a critical determinant of ...
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Arrested oocytes do not enter the subsequent stage, anaphase I. DNA double strand breaks, UVB and ionizing radiation induced DNA damage cause an effective block to anaphase promoting complex activity. [57] This checkpoint may help prevent oocytes with damaged DNA from progressing to become fertilizable mature eggs. [57]