Meiosis consists of

Options

A. two cell divisions without any DNA replication
B. two cell divisions in which chromosome number is reduced to half
C. two cell devisions with only two rounds of chromosome replication
D. a single cell division with chromosome replication.

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 four haploid cells from one diploid cell.

2. **Phases of Meiosis**: Meiosis consists of two main stages:
- **Meiosis I**: This is the first division where homologous chromosomes are separated.
- **Meiosis II**: This is the second division where sister chromatids are separated.

3. **Chromosome Replication**: Before meiosis begins, the DNA is replicated during the S phase of interphase, resulting in duplicated chromosomes. However, there is no further DNA replication during the two meiotic divisions.

4. **Outcome of Meiosis**: The end result of meiosis is four haploid cells, each containing half the number of chromosomes compared to the original diploid cell. This reduction is crucial for sexual reproduction, ensuring that when gametes fuse during fertilization, the resulting zygote has the correct diploid number.

5. **Analyzing the Options**:
- **Option A**: "Two cell divisions without any DNA replication" - This is incorrect because DNA replication occurs once before meiosis begins.
- **Option B**: "Two cell divisions in which chromosome number is reduced to half" - This is correct as meiosis involves two divisions that reduce the chromosome number.
- **Option C**: "Two cell divisions with only two rounds of chromosome replication" - This is incorrect because there is only one round of chromosome replication before meiosis.
- **Option D**: "A single division with chromosome replication" - This is incorrect as meiosis consists of two divisions.

6. **Conclusion**: Based on the analysis, the correct answer is **Option B**: "Two cell divisions in which chromosome number is reduced to half."