During ovulation, the secondary oocyte resides at what specific stage of meiosis?
**Core Concept**
Meiosis is a specialized type of cell division that results in the production of gametes (sperm or eggs) in sexually reproducing organisms. It is a two-part process, meiosis I and meiosis II, which are initiated in the female and male reproductive systems. During ovulation, the secondary oocyte is arrested at a specific stage of meiosis, awaiting fertilization.
**Why the Correct Answer is Right**
The secondary oocyte is arrested at metaphase II of meiosis II. This stage is characterized by the alignment of chromosomes at the metaphase plate, awaiting the signal for the start of anaphase II. The secondary oocyte remains in this arrested state until fertilization occurs, when it completes meiosis II. The completion of meiosis II results in the formation of a mature ovum (egg cell) and a first polar body, which is released from the oocyte.
**Why Each Wrong Option is Incorrect**
**Option A:** Prophase I - This stage occurs during the first meiotic division, not the second, and is not relevant to the state of the secondary oocyte during ovulation.
**Option B:** Anaphase I - This stage also occurs during the first meiotic division and is not relevant to the state of the secondary oocyte during ovulation.
**Option C:** Telophase I - This stage is also part of the first meiotic division and is not relevant to the state of the secondary oocyte during ovulation.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the secondary oocyte remains arrested at metaphase II of meiosis II until fertilization, highlighting the importance of the fertilization process in completing meiosis and resulting in a mature ovum.
**Correct Answer:** C. Metaphase II.