How many nucleosomes are found in helical coil of 30 nm chromatin fibre

Options

A. 10
B. 12
C. `06`
D. `09`

Explanation

To determine how many nucleosomes are found in a helical coil of 30 nm chromatin fiber, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Nucleosomes**:
- Nucleosomes are the basic unit of DNA packaging in eukaryotes. Each nucleosome consists of a segment of DNA wrapped around a core of histone proteins.

2. **Identify the Size of Nucleosomes**:
- Each nucleosome contains approximately 166 base pairs of DNA. This is important for calculating how many nucleosomes fit into a given length of DNA.

3. **Recognize the Chromatin Fiber Structure**:
- The chromatin fiber can exist in different forms. The 10 nm fiber represents the "beads on a string" form of chromatin where nucleosomes are spaced along the DNA.

4. **Understand the 30 nm Fiber Formation**:
- The 10 nm fiber coils further to form a more compact 30 nm fiber, which is referred to as a solenoid structure.

5. **Determine the Number of Nucleosomes in the 30 nm Fiber**:
- In the 30 nm chromatin fiber, it is known that approximately 6 nucleosomes are present per turn of the solenoid structure.

6. **Conclusion**:
- Therefore, the total number of nucleosomes found in a helical coil of 30 nm chromatin fiber is 6.

### Final Answer:
The number of nucleosomes in a helical coil of 30 nm chromatin fiber is **6 nucleosomes**.

---