Monozygotic twins are formed when:

Options

A. Two ova are fertilized simultaneously
B. Incomplete cleavage of zygote
C. First cleavage of zygote is followed by separation into two
D. Tehre is on cleavage.

Answer

To determine how monozygotic twins are formed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Monozygotic Twins**:
- Monozygotic twins, also known as identical twins, originate from a single fertilized egg (zygote). This means that they share the same genetic material.

2. **Fertilization Process**:
- Monozygotic twins begin their formation with the fertilization of one egg by one sperm, resulting in the formation of a zygote.

3. **Cleavage of the Zygote**:
- After fertilization, the zygote undergoes a series of cell divisions known as cleavage. This process involves the zygote dividing into smaller cells called blastomeres.

4. **Separation into Two Embryos**:
- In the case of monozygotic twins, during the cleavage process, the zygote divides and the resulting cells separate to form two distinct embryos. This typically happens after the first cleavage division.

5. **Conclusion**:
- Therefore, the correct answer to the question is that monozygotic twins are formed when the first cleavage of the zygote is followed by separation into two embryos.

### Final Answer:
- The correct option is **C: First cleavage of zygote is followed by separation into two.**

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