Chromosome number is reduced during meiosis because the process consists of-

Options

A. Two cell divisions without any chromosome replication
B. A single cell division without any chromosome replication
C. Two cell divisions in which half of the chromosomes are destroyed
D. Two cell divisions and only a single round of chromosome replication

Answer

To understand why the chromosome number is reduced during meiosis, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**: The cell cycle consists of several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis/Meiosis). In G1, the cell grows and prepares for DNA replication.

2. **DNA Replication**: During the S phase, the DNA is replicated. This means that each chromosome is duplicated, resulting in two sister chromatids for each chromosome. By the end of the S phase, the cell has doubled its genetic material.

3. **Meiosis Overview**: Meiosis is a specialized type of cell division that occurs in diploid cells to produce haploid gametes (sperm and eggs). It consists of two sequential divisions: Meiosis I and Meiosis II.

4. **Meiosis I**: In Meiosis I, homologous chromosomes (each consisting of two sister chromatids) are separated into two different cells. This is the reductional division where the chromosome number is halved. For example, if the original cell had 46 chromosomes, after Meiosis I, each daughter cell will have 23 chromosomes.

5. **Meiosis II**: In Meiosis II, the sister chromatids of each chromosome are separated. However, there is no further DNA replication before this division. This is similar to mitosis but occurs in the haploid cells produced from Meiosis I.

6. **Final Outcome**: After Meiosis II, the result is four haploid cells, each with half the original number of chromosomes. Thus, from one diploid cell, we end up with four haploid cells.

### Conclusion:
The reduction in chromosome number during meiosis occurs because there are two rounds of cell division (Meiosis I and Meiosis II) following only one round of DNA replication. This results in a halving of the chromosome number from diploid to haploid.