Select the incorrect pairing

Options

A. Mitochondria - Semiautonomous organelle
B. Stroma - Site of dark reaction
C. Centrioles - (9 + 2) array of microtubules
D. Axoneme - Core of eukaryotic flagella

Answer

To solve the question of selecting the incorrect pairing, we will analyze each option provided in the question step by step.

### Step 1: Analyze Mitochondria
- **Statement**: Mitochondria is a semi-autonomous organelle.
- **Explanation**: Mitochondria are indeed semi-autonomous organelles because they contain their own DNA and ribosomes, allowing them to produce some of their own proteins. They are also known for their role in ATP production, which is the energy currency of the cell.
- **Conclusion**: This pairing is correct.

### Step 2: Analyze Stroma
- **Statement**: Stroma is the site of dark reactions.
- **Explanation**: The stroma is the fluid-filled space in chloroplasts where the Calvin cycle (dark reactions) occurs. It does not contain thylakoids, which are the sites of light reactions. Therefore, the statement is accurate.
- **Conclusion**: This pairing is correct.

### Step 3: Analyze Centrioles
- **Statement**: Centrioles have a 9 plus 2 array of microtubules.
- **Explanation**: This statement is incorrect. Centrioles are composed of a 9 triplet arrangement of microtubules, not a 9 plus 2 arrangement. The 9 plus 2 arrangement is characteristic of cilia and flagella, not centrioles.
- **Conclusion**: This pairing is incorrect.

### Step 4: Analyze Axoneme
- **Statement**: Axoneme is the core of eukaryotic flagella.
- **Explanation**: The axoneme is indeed the structural core of eukaryotic flagella and cilia, consisting of a 9 plus 2 arrangement of microtubules. It plays a crucial role in the movement of these structures.
- **Conclusion**: This pairing is correct.

### Final Conclusion
After analyzing all the pairings, we find that the incorrect pairing is the one regarding centrioles, which is stated to have a 9 plus 2 array of microtubules. The correct structure of centrioles is a triplet arrangement of microtubules.

### Answer
The incorrect pairing is: **Centrioles - 9 plus 2 array of microtubules.**

---