A reaction fo granules content which harden the zona pellucida and ensures sure block to polyspermy is

Options

A. acrosomal reaction
B. cortical reaction
C. acrosin reaction
D. binding reaction

Explanation

**Step-by-Step Solution:**

1. **Understanding Key Terms**:
- **Granules Content**: These are cortical granules present in the egg's plasma membrane.
- **Zona Pellucida**: This is a protective layer surrounding the egg (ovum).
- **Polyspermy**: This is a condition where more than one sperm fertilizes an egg, which is not desirable.

2. **Fertilization Process**:
- When a sperm successfully penetrates the egg, fertilization occurs. This triggers a series of reactions in the egg.

3. **Cortical Reaction**:
- Immediately after fertilization, the egg undergoes a cortical reaction. This is a critical process that prevents polyspermy.

4. **Role of Cortical Granules**:
- The cortical granules, which are located beneath the egg's plasma membrane, fuse with the plasma membrane upon fertilization.

5. **Release of Enzymes**:
- The fusion of these granules leads to the release of enzymes into the space between the egg's plasma membrane and the zona pellucida.

6. **Hardening of Zona Pellucida**:
- The enzymes released from the cortical granules cause the zona pellucida to harden. This hardening acts as a barrier to prevent any additional sperm from entering the egg.

7. **Conclusion**:
- The reaction that hardens the zona pellucida and blocks polyspermy is known as the **cortical reaction**.

8. **Correct Answer**:
- Therefore, the correct answer to the question is **cortical reaction**.

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