When paternal and maternal chromosomes mutually exchange their materials in cell division, the event is called

Options

A. Bivalent formation
B. Recombination
C. Synapsis
D. Dyad formation

Answer

To solve the question regarding the event when paternal and maternal chromosomes mutually exchange their materials during cell division, we will analyze each option provided and determine the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding the Question**:
The question asks about the event in which paternal and maternal chromosomes exchange genetic material during cell division. This typically occurs during meiosis.

2. **Analyzing Option A - Bivalent Formation**:
- Bivalent formation occurs during the prophase I stage of meiosis, specifically in the pachytene stage.
- In this stage, homologous chromosomes pair up, but this does not specifically refer to the exchange of genetic material.
- **Conclusion**: This option is incorrect.

3. **Analyzing Option B - Recombination**:
- Recombination refers to the process where genetic material is exchanged between homologous chromosomes.
- This exchange leads to new combinations of alleles, which is crucial for genetic diversity.
- **Conclusion**: This option is correct.

4. **Analyzing Option C - Synapsis**:
- Synapsis is the process where homologous chromosomes pair closely together during prophase I of meiosis.
- While synapsis is important for the alignment of chromosomes, it does not specifically refer to the exchange of genetic material.
- **Conclusion**: This option is incorrect.

5. **Analyzing Option D - Dyad Formation**:
- Dyad formation refers to the pairing of sister chromatids during meiosis.
- This occurs later in the meiotic process and does not involve the exchange of genetic material between homologous chromosomes.
- **Conclusion**: This option is also incorrect.

6. **Final Conclusion**:
- After analyzing all the options, the only term that accurately describes the mutual exchange of genetic material between paternal and maternal chromosomes during cell division is **Recombination**.

### Answer:
The event when paternal and maternal chromosomes mutually exchange their materials in cell division is called **Recombination** (Option B).

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