The number of chromosomes in parents and offsprings of a particular species remains constant due to

Options

A. doubling of chromosomes after zygote formation
B. halving of chromosomes during gamete formation
C. doubling of chromosomes after gamete formation
D. halving of chromosomes after gamete formation

Explanation

### Step-by-Step Solution:

1. **Understanding Chromosome Number**:
- In sexually reproducing organisms, the number of chromosomes is maintained across generations. This means that the number of chromosomes in the parents is the same as in their offspring.

2. **Identifying Parental Chromosome Number**:
- Let’s denote the chromosome number in the parent cells as 2N (where N represents the number of chromosomes in a gamete).

3. **Formation of Gametes**:
- Gametes (sperm and egg) are produced through a process called meiosis. This is a type of cell division that reduces the chromosome number by half.

4. **Meiosis Process**:
- During meiosis, the diploid parent cell (2N) undergoes two rounds of division, resulting in four haploid gametes, each with N chromosomes.

5. **Fertilization**:
- When a male gamete (N) fuses with a female gamete (N) during fertilization, they form a zygote. The zygote now has a diploid chromosome number of 2N.

6. **Conclusion**:
- This process of halving the chromosome number during gamete formation (meiosis) ensures that the chromosome number remains constant from parents to offspring. Therefore, the answer to the question is option B: halving of chromosomes during gamete formation.