Figure 1.

Scheme showing the single phases of meiosis I and II. Every girl (as most of the mammalian species) is born with a defined set of primordial follicles containing the oocytes, however, already at the onset of puberty this ovarian pool has diminished substantially. The oocytes are arrested in prophase I, and from menarche to menopause some of the oocytes are selected for further development when resumption of meiosis occurs. Thereby, the “waiting time” of an oocyte to be fertilized after reaching metaphase II could last many years, nowadays even up to 35 years or more, depending on women’s wish to become pregnant. In consequence, the chance and number of telomeric DNA damage and telomere dysfunction increase with advancing maternal age of the oocyte.