A reduction step during meiosis is important because -

Options

A. It returns the chromosome number to normal before fertilization.
B. There is a mechanism for this
C. Only one copy of each chromosome is necessary
D. Otherwise chromosome copies would double each fertilization

Answer

**Step-by-Step Solution:**

1. **Understanding Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of gametes (sperm and eggs). It consists of two main stages: Meiosis I and Meiosis II.

2. **Chromosome Number**: In organisms, cells typically have a diploid (2N) number of chromosomes. For example, if an organism has 2N = 46 chromosomes, it has 23 pairs of chromosomes.

3. **Meiosis I - Reduction Division**: During Meiosis I, homologous chromosomes are separated. This is the reduction step where the diploid cell (2N) divides into two haploid cells (N), each containing half the number of chromosomes.

4. **Meiosis II - Equational Division**: Meiosis II resembles mitosis, where the two haploid cells divide again, resulting in four haploid cells (N). Each of these cells is a gamete.

5. **Importance of Reduction Step**: The reduction step is crucial because it ensures that when two gametes fuse during fertilization, the resulting zygote restores the diploid number (2N). If the gametes did not undergo this reduction, and remained diploid (2N), the zygote formed after fertilization would have a tetraploid (4N) chromosome number.

6. **Consequences of Not Having a Reduction Step**: If the chromosome number doubled with each fertilization (i.e., if gametes were diploid instead of haploid), the chromosome number in the offspring would increase exponentially with each generation, leading to genetic instability and potential viability issues.

7. **Conclusion**: Therefore, the reduction step during meiosis is essential to maintain the stable chromosome number across generations and prevent doubling of chromosome numbers with each fertilization.

**Final Answer**: A reduction step during meiosis is important because it prevents the doubling of chromosome numbers with each fertilization, ensuring that the zygote maintains the correct diploid number of chromosomes.

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