At what stage does the primary oocyte arrest during meiosis?

The primary oocyte is arrested during meiosis at prophase I. This arrest occurs at the diplotene stage of prophase I and can last for years, often until ovulation during a woman's reproductive life. During this phase, the chromatin condenses, and the homologous chromosomes pair up, forming tetrads through the process of synapsis. It is noteworthy that this arrest reflects the complex regulatory mechanisms of ovarian follicle development where primary oocytes remain dormant until they receive appropriate hormonal signals to resume meiosis in response to the menstrual cycle. Thus, the primary oocyte's arrest at prophase I is a crucial phase in oocyte maturation that ultimately influences fertility and reproductive timing.