Select an incorrect statement w.r.t cell cycle

Options

A. Duplication of genes occurs twice in meiosis
B. Karyokinesis occurs twice during meiotic division
C. Cyclins are proteins that activate protein kinases to regulate the cell cycle
D. After telophase-I, chromosome number is reduced to half.

Answer

To solve the question of selecting an incorrect statement with respect to the cell cycle, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Cell Cycle**: The cell cycle consists of several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis or Meiosis). During the S phase, DNA replication occurs.

2. **Analyze Option A**:
- **Statement**: "Duplication of genes occurs twice in meiosis."
- **Evaluation**: This statement is incorrect because gene duplication (DNA replication) occurs only once during the S phase of interphase before meiosis begins. Therefore, this option is indeed incorrect.

3. **Analyze Option B**:
- **Statement**: "Karyokinesis occurs twice during meiotic division."
- **Evaluation**: This statement is correct. Karyokinesis, which is the division of the nucleus, occurs during both meiosis I and meiosis II.

4. **Analyze Option C**:
- **Statement**: "Cyclins are proteins that activate protein kinases to regulate the cell cycle."
- **Evaluation**: This statement is correct. Cyclins are indeed proteins that activate cyclin-dependent kinases (CDKs), which play a crucial role in regulating the cell cycle.

5. **Analyze Option D**:
- **Statement**: "After telophase I, chromosome number is reduced to half."
- **Evaluation**: This statement is correct. Meiosis is a reductional division, meaning that after telophase I, the chromosome number is halved.

6. **Conclusion**:
- The incorrect statement with respect to the cell cycle is **Option A**: "Duplication of genes occurs twice in meiosis."

### Final Answer:
The correct answer is **Option A**.

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