Constancy of the chromosome number in sexually produring generation is brought by the process of

Options

A. Meiosis
B. Mitosis
C. Amitosis
D. None

Answer

To answer the question regarding how the constancy of chromosome number in sexually reproducing generations is maintained, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Chromosome Number**:
- In sexually reproducing organisms, the chromosome number is a crucial aspect of genetic continuity. Each organism has a specific number of chromosomes that are maintained across generations.

2. **Types of Cell Division**:
- There are two main types of cell division: mitosis and meiosis.
- Mitosis is responsible for growth and repair, producing two identical daughter cells with the same chromosome number as the parent cell.
- Meiosis, on the other hand, is a special type of cell division that occurs in the formation of gametes (sperm and egg cells).

3. **Meiosis and Reduction Division**:
- Meiosis is known as a reduction division because it reduces the chromosome number by half.
- For example, if a parent cell has 36 chromosomes, meiosis will produce gametes that each contain 18 chromosomes (haploid).

4. **Formation of Gametes**:
- During sexual reproduction, male and female gametes (sperm and egg) are formed through meiosis. Each gamete carries half the number of chromosomes (haploid).
- When fertilization occurs, the male and female gametes combine to form a diploid zygote, restoring the original chromosome number.

5. **Constancy of Chromosome Number**:
- The process of meiosis ensures that the chromosome number remains constant across generations.
- The diploid zygote formed after fertilization will develop into an organism with the same chromosome number as its parents.

6. **Conclusion**:
- Therefore, the constancy of chromosome number in sexually reproducing generations is maintained by the process of meiosis.

### Final Answer:
The constancy of the chromosome number in sexually reproducing generations is brought by the process of **meiosis**.

---