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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]
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 ...
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
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]
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]
Secondary oocytes are the immature ovum shortly after ovulation, to fertilization, where it turns into an ootid. Thus, the time as a secondary oocyte is measured in days. Thus, the time as a secondary oocyte is measured in days.