Which of these pairs are incorrectly clubbed together?

Options

A. Cells in adult animals which do not divide - Heart cells
B. Equational division - Mitosis
C. Disc shaped structures at The surface of centromere - kinetochores
D. Initiation of assembly of mitotic spindle - Mitotic metaphase

Answer

To solve the question of which pairs are incorrectly clubbed together, we will analyze each option step by step.

### Step 1: Analyze Option A
**Statement:** Cells in adult animals which do not divide: heart cells.

**Explanation:**
Heart cells (cardiomyocytes) are known to have a very limited capacity to divide in adult animals. They primarily remain in a differentiated state and do not undergo mitosis. Therefore, this statement is correct.

### Step 2: Analyze Option B
**Statement:** Equational division: mitosis.

**Explanation:**
Mitosis is indeed an equational division where the daughter cells receive an equal number of chromosomes as the parent cell. This statement is correct.

### Step 3: Analyze Option C
**Statement:** Disc-shaped structures of the surface of centromere: kinetochores.

**Explanation:**
Kinetochores are protein complexes that assemble on the centromere of a chromosome and are involved in the movement of chromosomes during cell division. This statement is correct.

### Step 4: Analyze Option D
**Statement:** Initiation of assembly of mitotic spindle: mitotic metaphase.

**Explanation:**
The assembly of the mitotic spindle actually begins in prophase, not metaphase. During metaphase, the spindle apparatus is fully formed, and chromosomes are aligned at the metaphase plate. Therefore, this statement is incorrect.

### Conclusion
After analyzing all the options, we find that the incorrectly clubbed pair is **Option D**: Initiation of assembly of mitotic spindle which is mitotic metaphase.

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