| Feature | Primary Oocyte | Secondary Oocyte |
|---|---|---|
| Ploidy | Diploid (2n) | Haploid (n) |
| Arrest stage | Prophase I | Metaphase II |
| When arrested | During fetal life (before birth) | At ovulation |
| What breaks arrest | LH surge | Sperm penetration |
| Duration of arrest | ~12–50 years (fetal life to ovulation) | ~12–24 hours (ovulation to fertilization) |
| Meiotic division just completed | None — awaiting meiosis I | Meiosis I complete |
| Product after arrest breaks | Secondary oocyte + Polar Body I | Mature ovum + Polar Body II |
| NEET trap | Don't confuse with metaphase II | Don't say "meiosis II at ovulation" |
Mnemonic: "P-P, S-M" — Primary = Prophase; Secondary = Metaphase