Cyclin Dependent kinases (CDKs)

Options

A. Act as mitotic poisons
B. Cause disassembly of the mircrotubules
C. Control various phases of cell cycle
D. Arrest cell division due to non-formation of spindle

Answer

### Step-by-Step Solution:

1. **Understanding Cyclin-Dependent Kinases (CDKs)**:
- CDKs are a family of protein kinases that play a crucial role in regulating the cell cycle. They are activated by binding to cyclins, forming a cyclin-CDK complex.

2. **Role of Cyclin-CDK Complex**:
- The cyclin-CDK complex is essential for the progression through various phases of the cell cycle. CDKs phosphorylate specific target proteins that are necessary for the cell cycle's advancement.

3. **Presence of CDKs in Animal Cells**:
- In animal cells, there are at least nine different CDKs, out of which four are directly involved in the regulation of the cell cycle.

4. **Evaluating the Options**:
- **Option A: Act as a mitotic poison** - This is incorrect. CDKs do not act as mitotic poisons; instead, they facilitate the cell cycle progression.
- **Option B: Cause disassembly of microtubules** - This is also incorrect. While microtubule dynamics are important for cell division, CDKs do not cause disassembly of microtubules.
- **Option C: Control various phases of the cell cycle** - This is correct. CDKs regulate the cell cycle by phosphorylating proteins involved in different phases.
- **Option D: Arrest cell division due to non-formation of spindle** - This is incorrect. CDKs do not arrest cell division; they promote it.

5. **Conclusion**:
- The correct answer is **Option C: Control various phases of the cell cycle**.