Which of the two enents restore the normal number of chromosomes in life cycle?

Options

A. Mitosis and Meiosis
B. Meiosis and fertilisation
C. Fertilisation and mitosis
D. Only meiosis

Answer

To answer the question "Which of the two events restore the normal number of chromosomes in the life cycle?", we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Chromosome Number**:
- In a typical life cycle, organisms have a specific number of chromosomes that are maintained through various stages of development. This number can be diploid (2n) or haploid (n).

2. **Role of Meiosis**:
- Meiosis is the process that reduces the chromosome number by half. It occurs in germ cells to produce gametes (sperm and egg cells). For example, if an organism has a diploid number of 46 chromosomes, meiosis will produce gametes with 23 chromosomes each.

3. **Role of Fertilization**:
- Fertilization is the process where a male gamete (sperm) and a female gamete (egg) fuse to form a zygote. This zygote restores the diploid number of chromosomes. Continuing the previous example, when the sperm (23 chromosomes) fertilizes the egg (23 chromosomes), the resulting zygote will have 46 chromosomes.

4. **Conclusion**:
- Therefore, the two events that restore the normal number of chromosomes in the life cycle are **meiosis** (which reduces the chromosome number) and **fertilization** (which restores the chromosome number).

5. **Final Answer**:
- The correct answer to the question is **meiosis and fertilization**.