Meiosis-I is reductional division. Meiosis-II is equational division due to

Options

A. pairing of homologous chromosomes
B. crossing over
C. separation of chromatids
D. disjunction of homologous chromosomes

Explanation

To understand why Meiosis-I is a reductional division and Meiosis-II is an equational division, we need to analyze the processes that occur during each phase of meiosis.

### Step-by-Step Solution:

1. **Definition of Meiosis**:
- Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four haploid cells from one diploid cell. It consists of two main stages: Meiosis I and Meiosis II.

2. **Meiosis I - Reductional Division**:
- In Meiosis I, the cell starts as a diploid (2n) and undergoes a series of stages (prophase I, metaphase I, anaphase I, telophase I).
- During **anaphase I**, homologous chromosomes (each consisting of two sister chromatids) are separated and pulled to opposite poles of the cell. This separation reduces the chromosome number from diploid (2n) to haploid (n).
- Therefore, Meiosis I is termed a **reductional division** because it reduces the chromosome number.

3. **Meiosis II - Equational Division**:
- Meiosis II follows Meiosis I and resembles mitosis. The cells produced in Meiosis I are haploid (n).
- In Meiosis II, the sister chromatids of each chromosome are separated during **anaphase II** and move towards opposite poles.
- Since the cells are already haploid, the chromosome number remains the same after Meiosis II, resulting in four haploid cells.
- Hence, Meiosis II is termed an **equational division** because it does not change the chromosome number.

4. **Key Process**:
- The key process that differentiates Meiosis I from Meiosis II is the **separation of chromatids**. In Meiosis I, homologous chromosomes are separated, while in Meiosis II, sister chromatids are separated.
- This distinction is crucial in understanding why Meiosis I is reductional and Meiosis II is equational.

5. **Conclusion**:
- The correct answer to the question is **C. Separation of chromatids**, as this process is what dictates the difference between the two types of divisions.