Spindle microtubules composed of :–

Options

A. Actin filament
B. 95% dynein and 5% DNA
C. 95–97% tubulin and 3–5% RNA
D. Collagen and elastin protein

Answer

To answer the question "Spindle microtubules composed of:", we need to understand the structure and composition of spindle microtubules during cell division. Here’s a step-by-step solution:

### Step 1: Understand the Composition of Spindle Microtubules
Spindle microtubules are primarily composed of tubulin proteins. Tubulin exists in two forms: alpha-tubulin and beta-tubulin. These two types of tubulin proteins polymerize to form long, hollow tubes known as microtubules.

**Hint:** Think about the basic building blocks of microtubules and their types.

### Step 2: Identify the Role of Spindle Microtubules
During cell division, spindle microtubules play a crucial role in separating chromosomes. They attach to the kinetochores of chromosomes and help in their movement towards opposite poles of the cell.

**Hint:** Consider the function of these microtubules during the phases of cell division.

### Step 3: Recognize the Types of Microtubules in Spindle Formation
There are three types of microtubules involved in spindle formation:
1. **Kinetochore microtubules** - attach to the kinetochores of chromosomes.
2. **Polar microtubules** - extend from one pole of the spindle to the other, helping to push the spindle poles apart.
3. **Astral microtubules** - help anchor the spindle apparatus to the cell membrane.

**Hint:** Remember the different types of microtubules and their specific roles during mitosis.

### Step 4: Conclude the Composition
In summary, spindle microtubules are composed of tubulin proteins that assemble into microtubules, which are essential for the proper segregation of chromosomes during cell division.

**Hint:** Focus on the primary protein that makes up the microtubules and their structural significance.

### Final Answer:
Spindle microtubules are composed of tubulin proteins (alpha-tubulin and beta-tubulin).