Which histone is absent in a nucleosome?

Options

A. `H_1`
B. `H_2`
C. ` H_3 A `
D. `H_4`

Answer

To solve the question "Which histone is absent in a nucleosome?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of a Nucleosome**:
- A nucleosome is the fundamental unit of chromatin, consisting of a segment of DNA wrapped around a core of histone proteins.

2. **Identify the Types of Histones**:
- There are five main types of histone proteins: H1, H2A, H2B, H3, and H4.
- Among these, H2A, H2B, H3, and H4 are the core histones that form the nucleosome core.

3. **Determine the Role of Each Histone**:
- The core histones (H2A, H2B, H3, and H4) form an octamer around which DNA is wrapped.
- H1 is known as the linker histone, which is involved in the higher-order structure of chromatin but is not part of the nucleosome core.

4. **Conclude Which Histone is Absent**:
- Since H1 is not part of the nucleosome core structure, it is the histone that is absent in a nucleosome.

### Final Answer:
The histone that is absent in a nucleosome is **H1**.

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