Which one is not true of centriole?

Options

A. A) 9+2 arrangement
B. B) 9+0 arrangement
C. C) Non-membranous organelles
D. D) Associated with MTOCs

Answer

### Step-by-Step Solution

1. **Understanding Centrioles**: Centrioles are microscopic structures made up of microtubules. They play a crucial role in cell division and the formation of structures like astral rays and basal bodies.

2. **Structure of Centrioles**: A pair of centrioles is referred to as a diplosome. These centrioles are arranged at right angles to each other and are surrounded by a cytoplasmic layer known as the centrosphere. Together, they form a structure called the centrosome.

3. **Characteristics of Centrioles**:
- Centrioles are non-membranous organelles.
- They do not exhibit the 9 + 2 arrangement typical of cilia and flagella. Instead, they have a 9 + 0 arrangement, meaning they consist of nine triplet microtubules with no central pair.

4. **Role in Cell Division**: Centrioles are classified as microtubule organizing centers (MTOCs) and are essential for the proper organization of microtubules during cell division.

5. **Identifying the False Statement**: Given the characteristics of centrioles, the statement that is not true about them is that they have a 9 + 2 arrangement, which is a feature of cilia and flagella, not centrioles.

### Conclusion
The statement that is not true of centrioles is that they have a 9 + 2 arrangement.

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