Main protein of mitotic spindle fibres is

Options

A. Tubulin
B. Myosin
C. Tropomyosin
D. Dynein

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the main protein that makes up the mitotic spindle fibers during cell division.

2. **Identifying the Options**: The options provided are:
- Option 1: Tubulin
- Option 2: Myosin
- Option 3: Tropomyosin
- Option 4: Dynein

3. **Analyzing Each Option**:
- **Option 1: Tubulin**: This is a protein that forms microtubules, which are essential components of the mitotic spindle. Tubulin is synthesized during the G2 phase of interphase and is crucial for the formation of spindle fibers.
- **Option 2: Myosin**: This protein is involved in muscle contraction and interacts with actin filaments, but it is not a component of the mitotic spindle.
- **Option 3: Tropomyosin**: This protein also plays a role in muscle contraction by regulating actin filaments, but it is not related to the mitotic spindle.
- **Option 4: Dynein**: This is a motor protein that moves along microtubules but does not form the spindle fibers themselves.

4. **Conclusion**: Based on the analysis, the correct answer is **Option 1: Tubulin**, as it is the main protein that makes up the mitotic spindle fibers.

**Final Answer**: Tubulin

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