Secodnary oocyte is formed

Options

A. Before ovum maturation
B. After mitosis of germinal cells
C. After fertilization
D. Before fertilization

Answer

To determine when the secondary oocyte is formed, we need to analyze the options provided and understand the process of oocyte development.

### Step-by-Step Solution:

1. **Understanding Oocyte Development**:
- The primary oocyte undergoes meiosis to eventually form a secondary oocyte. This process occurs in the ovaries during oogenesis.

2. **Meiosis Process**:
- Oogenesis begins with the primary oocyte, which is arrested in prophase I of meiosis until puberty. Upon maturation, the primary oocyte completes the first meiotic division to form a secondary oocyte and a polar body.

3. **Timing of Secondary Oocyte Formation**:
- The secondary oocyte is formed just before ovulation. It is released from the mature Graafian follicle during the menstrual cycle.

4. **Analyzing the Options**:
- **Option A: Before maturation** - This is incorrect because the secondary oocyte is formed after the maturation of the primary oocyte.
- **Option B: After mitosis of germinal cells** - This is incorrect as the secondary oocyte is formed after meiosis, not mitosis.
- **Option C: After fertilization** - This is incorrect because the secondary oocyte is formed before fertilization occurs.
- **Option D: Before fertilization** - This is correct because the secondary oocyte is indeed formed before fertilization takes place.

5. **Conclusion**:
- Based on the analysis, the correct answer is **Option D: Before fertilization**.