In tetrad, the number of non cross over chromatids is normally :–

Options

A. Four
B. Two
C. One
D. None

Answer

To solve the question regarding the number of non-crossover chromatids in a tetrad, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Tetrads**: A tetrad consists of four chromatids formed during the prophase of meiosis when homologous chromosomes pair up. Each homologous chromosome consists of two sister chromatids.

2. **Identifying Chromatids**: In a tetrad, there are two homologous chromosomes, and each of these chromosomes has two chromatids. Therefore, in total, there are four chromatids in a tetrad.

3. **Crossing Over**: During meiosis, crossing over can occur between homologous chromosomes. This means that some chromatids may exchange genetic material.

4. **Non-Crossover Chromatids**: Non-crossover chromatids are those that have not undergone crossing over. In a typical tetrad, after crossing over, there are usually two chromatids that have exchanged segments (crossover chromatids) and two chromatids that have not exchanged any segments (non-crossover chromatids).

5. **Conclusion**: Therefore, in a tetrad, the number of non-crossover chromatids is typically 2.

### Final Answer:
The number of non-crossover chromatids in a tetrad is **2**.

---