Spindle fibres are chemically

Options

A. Carbohydrates
B. Proteins
C. Proteins and carbohydrates
D. Proteins and fats

Answer

### Step-by-Step Solution:

1. **Understanding Spindle Fibers**: Spindle fibers are structures that play a crucial role during cell division, specifically in the process of mitosis and meiosis. They help in the separation of chromosomes.

2. **Identifying the Composition**: To determine what spindle fibers are chemically made of, we need to look at their composition. Spindle fibers are primarily composed of proteins.

3. **Key Protein Involved**: The main protein that makes up spindle fibers is tubulin. Tubulin is a globular protein that polymerizes to form microtubules, which are the structural components of spindle fibers.

4. **Percentage Composition**: It is noted that spindle fibers are made up of approximately 97% tubulin protein and about 3% RNA. This indicates that the predominant component is indeed protein.

5. **Conclusion**: Based on the information gathered, we can conclude that spindle fibers are primarily made of proteins, specifically tubulin.

6. **Final Answer**: Therefore, the correct answer to the question "Spindle fibres are chemically" is **proteins**.