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 video transcript step by step.

### Step 1: Analyze the first pairing - Mitochondria
- Mitochondria are described as semi-autonomous organelles because they possess their own DNA and ribosomes.
- They are responsible for ATP production through cellular respiration.
- **Conclusion**: This pairing is correct.

### Step 2: Analyze the second pairing - Stroma
- The stroma is indeed the site of the dark reactions (Calvin cycle) in photosynthesis, which occurs in the chloroplasts.
- It is where NADPH and ATP are produced, and it is distinct from the thylakoid membranes where light reactions occur.
- **Conclusion**: This pairing is correct.

### Step 3: Analyze the third pairing - Centrioles
- Centrioles are typically described as having a structure composed of microtubules arranged in a "9 + 0" pattern (nine triplets of microtubules) rather than the "9 + 2" pattern found in cilia and flagella.
- The "9 + 2" arrangement refers to the structure of cilia and flagella, not centrioles.
- **Conclusion**: This pairing is incorrect.

### Step 4: Analyze the fourth pairing - Axoneme
- The axoneme is the central core of eukaryotic flagella and cilia, and it does indeed have a "9 + 2" arrangement of microtubules.
- This structure is crucial for the movement of flagella and cilia.
- **Conclusion**: This pairing is correct.

### Final Conclusion
The incorrect pairing among the options provided is the third one, which states that centrioles have a "9 + 2" array of microtubules. Instead, centrioles have a "9 + 0" arrangement.