In what stage does the secondary oocyte arrest during meiosis?

The secondary oocyte arrests during meiosis at metaphase II. This stage is characterized by the alignment of the chromosomes at the metaphase plate, where they are ready for separation. The secondary oocyte remains in this arrested state until fertilization occurs. Once a sperm penetrates the oocyte, it completes meiosis II and leads to the formation of the mature ovum and a second polar body.

In contrast, prophase II is a stage that occurs earlier in meiosis, during which the chromosomes condense and the nuclear envelope begins to break down again after the completion of the first meiotic division. Telophase II occurs after the chromosomes have been separated and is involved in the formation of two separate nuclei for the resulting cells, but at this point, the secondary oocyte has already completed its arrest. Interphase I refers to the stage prior to meiosis, and during this time, the oocyte is in its primordial or growth phase, which does not pertain to the arrest seen in the secondary oocyte.