Crossing over takes place on:-

Options

A. Two stranded stage
B. Three stranded stage
C. One stranded stage
D. Four stranded stage

Answer

**Step-by-Step Solution:**

1. **Understanding Crossing Over**: Crossing over is a genetic process that occurs during meiosis where homologous chromosomes exchange segments of their genetic material. This leads to genetic variation in the resulting gametes.

2. **Identifying the Stage of Meiosis**: Crossing over specifically occurs during prophase I of meiosis. During this stage, homologous chromosomes pair up and form tetrads (groups of four chromatids).

3. **Analyzing the Options**:
- **Option 1: Two standard stage** - This is incorrect as crossing over does not occur here.
- **Option 2: Three standard stage** - This is also incorrect for the same reason.
- **Option 3: One standard stage** - This option is incorrect as well.
- **Option 4: Four standard stage** - This is the correct answer since crossing over occurs during prophase I when the homologous chromosomes are in tetrads.

4. **Conclusion**: The correct answer is option 4, as crossing over occurs during the four standard stage (prophase I of meiosis).

**Final Answer**: Crossing over takes place on the four standard stage (prophase I of meiosis).

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