Which of the following is not a part of a chromosome?

Options

A. DNA
B. Centriole
C. Centromere
D. Chromatin

Explanation

To answer the question "Which of the following is not a part of a chromosome?" we will analyze the options provided: DNA, Centromere, and Chromatin.

### Step-by-Step Solution:

1. **Understanding Chromosome Structure**:
- A chromosome is primarily made up of DNA and proteins, specifically histone proteins. The DNA is negatively charged, while histone proteins are positively charged.

2. **Formation of Nucleosomes**:
- DNA wraps around histone proteins to form a structure called a nucleosome. This is the basic unit of DNA packaging.

3. **Chromatin Formation**:
- When nucleosomes coil and fold, they form a substance known as chromatin. Chromatin is the material that makes up chromosomes.

4. **Identifying the Centromere**:
- The centromere is a specific region of the chromosome that is constricted. It plays a crucial role during cell division by holding sister chromatids together and is also made of DNA.

5. **Evaluating the Options**:
- **DNA**: This is a fundamental component of chromosomes.
- **Centromere**: This is a part of the chromosome structure.
- **Chromatin**: This is the form that DNA takes when it is packaged within the chromosome.

6. **Identifying the Odd One Out**:
- The question asks for the option that is not a part of a chromosome. Among the options given, the centriole is not a part of the chromosome structure. Instead, it is involved in cell division and helps in the formation of spindle fibers.

### Conclusion:
The correct answer is **Centriole**, as it is not a part of the chromosome.

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