Identify the incorrectly matched pair in the given options .

Options

A. DNA duplication - S - phase
B. Reductional division - Meiosis
C. Equational division - Mitosis
D. Crossing over - Sister chromatids of homologous chromosomes.

Answer

To solve the question of identifying the incorrectly matched pair from the given options, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: DNA duplication S phase**
- The S phase (Synthesis phase) is part of the cell cycle where DNA replication occurs. During this phase, the amount of DNA in the cell doubles, but the chromosome number remains the same.
- **Conclusion**: This option is correctly matched.

2. **Option B: Reduction division meiosis**
- Meiosis is indeed referred to as a reduction division because it reduces the chromosome number by half in the daughter cells compared to the mother cell.
- In meiosis, the chromosome number is halved from diploid (2N) to haploid (N).
- **Conclusion**: This option is correctly matched.

3. **Option C: Equational division mitosis**
- Mitosis is known as an equational division because the daughter cells produced have the same chromosome number and amount of DNA as the mother cell.
- The chromosome number and DNA content remain constant through mitosis.
- **Conclusion**: This option is correctly matched.

4. **Option D: Crossing over sister chromatids of non-homologous chromosomes**
- Crossing over occurs between non-sister chromatids of homologous chromosomes, not sister chromatids. Sister chromatids are identical copies of a chromosome that are joined together.
- The statement incorrectly describes the process, as crossing over does not occur between sister chromatids.
- **Conclusion**: This option is incorrectly matched.

### Final Answer:
The incorrectly matched pair is **Option D: Crossing over sister chromatids of non-homologous chromosomes**.

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